<?xml version="1.0" encoding="UTF-8"?>

<!--XBRL Document Created with Wdesk from Workiva-->
<!--Copyright 2023 Workiva-->
<!--r:be05419e-01fc-4fdd-85d3-65a951f29669,g:526eaf95-e615-4677-af99-78575a0d42e0-->
<link:linkbase xmlns:link="http://www.xbrl.org/2003/linkbase" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xbrldt="http://xbrl.org/2005/xbrldt" xsi:schemaLocation="http://www.xbrl.org/2003/linkbase http://www.xbrl.org/2003/xbrl-linkbase-2003-12-31.xsd">
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/all" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#all"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#hypercube-dimension"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#dimension-default"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#dimension-domain"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#domain-member"/>
  <link:roleRef roleURI="http://brilliantearth.com/role/Cover" xlink:type="simple" xlink:href="brlt-20230331.xsd#Cover"/>
  <link:definitionLink xlink:role="http://brilliantearth.com/role/Cover" xlink:type="extended" id="i54018230b6ce418c9220c4d8798659c3_Cover">
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentInformationLineItems_e0af3dfd-0ab3-4381-89ca-6b12bf104dec" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_DocumentInformationLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentType_b6e86229-d428-42bc-9a44-d206f497b353" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_DocumentType"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_e0af3dfd-0ab3-4381-89ca-6b12bf104dec" xlink:to="loc_dei_DocumentType_b6e86229-d428-42bc-9a44-d206f497b353" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentQuarterlyReport_32db8ea4-5d86-4b73-8ddc-a0e85c21e2a9" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_DocumentQuarterlyReport"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_e0af3dfd-0ab3-4381-89ca-6b12bf104dec" xlink:to="loc_dei_DocumentQuarterlyReport_32db8ea4-5d86-4b73-8ddc-a0e85c21e2a9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentPeriodEndDate_ff55ba1a-7b7f-4823-b613-28f6fe158bcd" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_DocumentPeriodEndDate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_e0af3dfd-0ab3-4381-89ca-6b12bf104dec" xlink:to="loc_dei_DocumentPeriodEndDate_ff55ba1a-7b7f-4823-b613-28f6fe158bcd" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentTransitionReport_152c4649-c50b-46ae-953f-91f245fb26a4" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_DocumentTransitionReport"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_e0af3dfd-0ab3-4381-89ca-6b12bf104dec" xlink:to="loc_dei_DocumentTransitionReport_152c4649-c50b-46ae-953f-91f245fb26a4" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityFileNumber_26bc035c-dae4-4ef2-b1c8-2fbd01209230" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_EntityFileNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_e0af3dfd-0ab3-4381-89ca-6b12bf104dec" xlink:to="loc_dei_EntityFileNumber_26bc035c-dae4-4ef2-b1c8-2fbd01209230" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityRegistrantName_01b6a7c9-5d1f-4472-ae51-081aef79327d" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_EntityRegistrantName"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_e0af3dfd-0ab3-4381-89ca-6b12bf104dec" xlink:to="loc_dei_EntityRegistrantName_01b6a7c9-5d1f-4472-ae51-081aef79327d" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityIncorporationStateCountryCode_e813dd1d-0fa0-4bc8-85ce-09277937153e" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_EntityIncorporationStateCountryCode"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_e0af3dfd-0ab3-4381-89ca-6b12bf104dec" xlink:to="loc_dei_EntityIncorporationStateCountryCode_e813dd1d-0fa0-4bc8-85ce-09277937153e" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityTaxIdentificationNumber_d2e3e853-0994-4795-87ab-4f349b4cf23a" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_EntityTaxIdentificationNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_e0af3dfd-0ab3-4381-89ca-6b12bf104dec" xlink:to="loc_dei_EntityTaxIdentificationNumber_d2e3e853-0994-4795-87ab-4f349b4cf23a" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressAddressLine1_87a30686-5c42-41ef-9a25-282a520eb9a0" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_EntityAddressAddressLine1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_e0af3dfd-0ab3-4381-89ca-6b12bf104dec" xlink:to="loc_dei_EntityAddressAddressLine1_87a30686-5c42-41ef-9a25-282a520eb9a0" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressAddressLine2_080c3a52-313f-48f1-b060-970547700c29" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_EntityAddressAddressLine2"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_e0af3dfd-0ab3-4381-89ca-6b12bf104dec" xlink:to="loc_dei_EntityAddressAddressLine2_080c3a52-313f-48f1-b060-970547700c29" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressCityOrTown_05f34145-ba7d-424e-b2a5-7cc5071aede4" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_EntityAddressCityOrTown"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_e0af3dfd-0ab3-4381-89ca-6b12bf104dec" xlink:to="loc_dei_EntityAddressCityOrTown_05f34145-ba7d-424e-b2a5-7cc5071aede4" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressStateOrProvince_57c79b78-4927-46a9-90ab-c126692e57c9" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_EntityAddressStateOrProvince"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_e0af3dfd-0ab3-4381-89ca-6b12bf104dec" xlink:to="loc_dei_EntityAddressStateOrProvince_57c79b78-4927-46a9-90ab-c126692e57c9" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressPostalZipCode_6b30a900-dd7f-45c3-b6cd-6c857283444c" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_EntityAddressPostalZipCode"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_e0af3dfd-0ab3-4381-89ca-6b12bf104dec" xlink:to="loc_dei_EntityAddressPostalZipCode_6b30a900-dd7f-45c3-b6cd-6c857283444c" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_CityAreaCode_9fd3f9e2-cce8-42c8-900c-88aabac2b0d6" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_CityAreaCode"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_e0af3dfd-0ab3-4381-89ca-6b12bf104dec" xlink:to="loc_dei_CityAreaCode_9fd3f9e2-cce8-42c8-900c-88aabac2b0d6" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_LocalPhoneNumber_14a703fe-a561-482d-a0a0-b7f218a4e467" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_LocalPhoneNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_e0af3dfd-0ab3-4381-89ca-6b12bf104dec" xlink:to="loc_dei_LocalPhoneNumber_14a703fe-a561-482d-a0a0-b7f218a4e467" xlink:type="arc" order="14"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_Security12bTitle_5cfc9760-4bc2-48f1-b3d9-42cb16e7cd5a" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_Security12bTitle"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_e0af3dfd-0ab3-4381-89ca-6b12bf104dec" xlink:to="loc_dei_Security12bTitle_5cfc9760-4bc2-48f1-b3d9-42cb16e7cd5a" xlink:type="arc" order="15"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_TradingSymbol_7f6eba50-9fd8-4394-a55d-eea8d2b654a8" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_TradingSymbol"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_e0af3dfd-0ab3-4381-89ca-6b12bf104dec" xlink:to="loc_dei_TradingSymbol_7f6eba50-9fd8-4394-a55d-eea8d2b654a8" xlink:type="arc" order="16"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_SecurityExchangeName_a17b94e9-12e7-425b-9cc1-a858dae5fe4d" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_SecurityExchangeName"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_e0af3dfd-0ab3-4381-89ca-6b12bf104dec" xlink:to="loc_dei_SecurityExchangeName_a17b94e9-12e7-425b-9cc1-a858dae5fe4d" xlink:type="arc" order="17"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityCurrentReportingStatus_ff8f450f-8bbf-4a1a-b834-22711cf28249" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_EntityCurrentReportingStatus"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_e0af3dfd-0ab3-4381-89ca-6b12bf104dec" xlink:to="loc_dei_EntityCurrentReportingStatus_ff8f450f-8bbf-4a1a-b834-22711cf28249" xlink:type="arc" order="18"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityInteractiveDataCurrent_c6ce47e9-d063-4733-b491-262dc5185bc0" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_EntityInteractiveDataCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_e0af3dfd-0ab3-4381-89ca-6b12bf104dec" xlink:to="loc_dei_EntityInteractiveDataCurrent_c6ce47e9-d063-4733-b491-262dc5185bc0" xlink:type="arc" order="19"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityFilerCategory_e79bd8a4-94a8-4ce2-9429-46abec89b3f4" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_EntityFilerCategory"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_e0af3dfd-0ab3-4381-89ca-6b12bf104dec" xlink:to="loc_dei_EntityFilerCategory_e79bd8a4-94a8-4ce2-9429-46abec89b3f4" xlink:type="arc" order="20"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntitySmallBusiness_e041425f-84f4-4f1b-9f0a-e2e1291b3f6c" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_EntitySmallBusiness"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_e0af3dfd-0ab3-4381-89ca-6b12bf104dec" xlink:to="loc_dei_EntitySmallBusiness_e041425f-84f4-4f1b-9f0a-e2e1291b3f6c" xlink:type="arc" order="21"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityEmergingGrowthCompany_46239507-9068-4cda-9ffb-de5f02cffe5a" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_EntityEmergingGrowthCompany"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_e0af3dfd-0ab3-4381-89ca-6b12bf104dec" xlink:to="loc_dei_EntityEmergingGrowthCompany_46239507-9068-4cda-9ffb-de5f02cffe5a" xlink:type="arc" order="22"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityExTransitionPeriod_38ff3ae6-38f5-4956-8adb-6272610d20bc" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_EntityExTransitionPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_e0af3dfd-0ab3-4381-89ca-6b12bf104dec" xlink:to="loc_dei_EntityExTransitionPeriod_38ff3ae6-38f5-4956-8adb-6272610d20bc" xlink:type="arc" order="23"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityShellCompany_e1572935-960a-4fc0-9555-9b0541f365eb" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_EntityShellCompany"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_e0af3dfd-0ab3-4381-89ca-6b12bf104dec" xlink:to="loc_dei_EntityShellCompany_e1572935-960a-4fc0-9555-9b0541f365eb" xlink:type="arc" order="24"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityCommonStockSharesOutstanding_4751b504-a42f-4c3b-ac6c-a1720aa7ee6d" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_EntityCommonStockSharesOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_e0af3dfd-0ab3-4381-89ca-6b12bf104dec" xlink:to="loc_dei_EntityCommonStockSharesOutstanding_4751b504-a42f-4c3b-ac6c-a1720aa7ee6d" xlink:type="arc" order="25"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityCentralIndexKey_f4e68305-20d2-4773-998a-03f5514634ba" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_EntityCentralIndexKey"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_e0af3dfd-0ab3-4381-89ca-6b12bf104dec" xlink:to="loc_dei_EntityCentralIndexKey_f4e68305-20d2-4773-998a-03f5514634ba" xlink:type="arc" order="26"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_CurrentFiscalYearEndDate_c9622ee8-836d-41cc-891b-e110e3d84228" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_CurrentFiscalYearEndDate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_e0af3dfd-0ab3-4381-89ca-6b12bf104dec" xlink:to="loc_dei_CurrentFiscalYearEndDate_c9622ee8-836d-41cc-891b-e110e3d84228" xlink:type="arc" order="27"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentFiscalYearFocus_634a118e-e8d4-4391-ab5b-677528b3e7ca" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_DocumentFiscalYearFocus"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_e0af3dfd-0ab3-4381-89ca-6b12bf104dec" xlink:to="loc_dei_DocumentFiscalYearFocus_634a118e-e8d4-4391-ab5b-677528b3e7ca" xlink:type="arc" order="28"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentFiscalPeriodFocus_5f49dfbb-c217-4eb5-87a7-87fd95d582d8" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_DocumentFiscalPeriodFocus"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_e0af3dfd-0ab3-4381-89ca-6b12bf104dec" xlink:to="loc_dei_DocumentFiscalPeriodFocus_5f49dfbb-c217-4eb5-87a7-87fd95d582d8" xlink:type="arc" order="29"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_AmendmentFlag_ea834933-59be-4b8d-a179-b362e583d886" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_AmendmentFlag"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_e0af3dfd-0ab3-4381-89ca-6b12bf104dec" xlink:to="loc_dei_AmendmentFlag_ea834933-59be-4b8d-a179-b362e583d886" xlink:type="arc" order="30"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentInformationTable_bdff9822-7a25-4c61-b649-78c88d0c5425" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_DocumentInformationTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_dei_DocumentInformationLineItems_e0af3dfd-0ab3-4381-89ca-6b12bf104dec" xlink:to="loc_dei_DocumentInformationTable_bdff9822-7a25-4c61-b649-78c88d0c5425" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementClassOfStockAxis_c449ad90-b914-49b8-9e3e-1a25a56164c7" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StatementClassOfStockAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_dei_DocumentInformationTable_bdff9822-7a25-4c61-b649-78c88d0c5425" xlink:to="loc_us-gaap_StatementClassOfStockAxis_c449ad90-b914-49b8-9e3e-1a25a56164c7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_c449ad90-b914-49b8-9e3e-1a25a56164c7_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementClassOfStockAxis_c449ad90-b914-49b8-9e3e-1a25a56164c7" xlink:to="loc_us-gaap_ClassOfStockDomain_c449ad90-b914-49b8-9e3e-1a25a56164c7_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_51604144-d243-4584-a505-1fc29603183a" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementClassOfStockAxis_c449ad90-b914-49b8-9e3e-1a25a56164c7" xlink:to="loc_us-gaap_ClassOfStockDomain_51604144-d243-4584-a505-1fc29603183a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonClassAMember_be9fa7de-8492-4d3e-885c-e0233a11bdf6" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CommonClassAMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_51604144-d243-4584-a505-1fc29603183a" xlink:to="loc_us-gaap_CommonClassAMember_be9fa7de-8492-4d3e-885c-e0233a11bdf6" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonClassBMember_ea758801-4945-4c5e-be50-c69bbcbcc29c" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CommonClassBMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_51604144-d243-4584-a505-1fc29603183a" xlink:to="loc_us-gaap_CommonClassBMember_ea758801-4945-4c5e-be50-c69bbcbcc29c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonClassCMember_b5ee1254-ed5c-40f0-b51c-9045a15b7cdb" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CommonClassCMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_51604144-d243-4584-a505-1fc29603183a" xlink:to="loc_us-gaap_CommonClassCMember_b5ee1254-ed5c-40f0-b51c-9045a15b7cdb" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://brilliantearth.com/role/UNAUDITEDCONDENSEDCONSOLIDATEDBALANCESHEETS" xlink:type="simple" xlink:href="brlt-20230331.xsd#UNAUDITEDCONDENSEDCONSOLIDATEDBALANCESHEETS"/>
  <link:definitionLink xlink:role="http://brilliantearth.com/role/UNAUDITEDCONDENSEDCONSOLIDATEDBALANCESHEETS" xlink:type="extended" id="i327e70d77a39416ebc6f549f987845f1_UNAUDITEDCONDENSEDCONSOLIDATEDBALANCESHEETS">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_909a7fbc-e7fb-4873-886f-b38180dfcb63" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StatementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetsAbstract_6a113c8d-ed83-4a2b-b58f-2619bda6b36a" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AssetsAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_909a7fbc-e7fb-4873-886f-b38180dfcb63" xlink:to="loc_us-gaap_AssetsAbstract_6a113c8d-ed83-4a2b-b58f-2619bda6b36a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetsCurrentAbstract_6a21ab1f-1672-45e7-8d53-2d8ce7ec58a2" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AssetsCurrentAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_6a113c8d-ed83-4a2b-b58f-2619bda6b36a" xlink:to="loc_us-gaap_AssetsCurrentAbstract_6a21ab1f-1672-45e7-8d53-2d8ce7ec58a2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashAndCashEquivalentsAtCarryingValue_ea8a95d4-506a-4192-aad7-ca5d0891ad7d" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CashAndCashEquivalentsAtCarryingValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsCurrentAbstract_6a21ab1f-1672-45e7-8d53-2d8ce7ec58a2" xlink:to="loc_us-gaap_CashAndCashEquivalentsAtCarryingValue_ea8a95d4-506a-4192-aad7-ca5d0891ad7d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedCash_1f7f7b19-31f7-4712-9b62-5942a841b3b2" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_RestrictedCash"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsCurrentAbstract_6a21ab1f-1672-45e7-8d53-2d8ce7ec58a2" xlink:to="loc_us-gaap_RestrictedCash_1f7f7b19-31f7-4712-9b62-5942a841b3b2" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InventoryNet_924b0625-8ab7-4954-8d86-21e592add63b" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_InventoryNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsCurrentAbstract_6a21ab1f-1672-45e7-8d53-2d8ce7ec58a2" xlink:to="loc_us-gaap_InventoryNet_924b0625-8ab7-4954-8d86-21e592add63b" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PrepaidExpenseAndOtherAssetsCurrent_5ccd6d89-45a7-4cd5-92de-f9f04c70d754" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_PrepaidExpenseAndOtherAssetsCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsCurrentAbstract_6a21ab1f-1672-45e7-8d53-2d8ce7ec58a2" xlink:to="loc_us-gaap_PrepaidExpenseAndOtherAssetsCurrent_5ccd6d89-45a7-4cd5-92de-f9f04c70d754" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetsCurrent_dd43b9c0-cdec-469b-ba03-df142614262f" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AssetsCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsCurrentAbstract_6a21ab1f-1672-45e7-8d53-2d8ce7ec58a2" xlink:to="loc_us-gaap_AssetsCurrent_dd43b9c0-cdec-469b-ba03-df142614262f" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentNet_e80d00da-ed30-43f6-945f-0833f9a8fec6" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_PropertyPlantAndEquipmentNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_6a113c8d-ed83-4a2b-b58f-2619bda6b36a" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentNet_e80d00da-ed30-43f6-945f-0833f9a8fec6" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredIncomeTaxAssetsNet_0aa1438b-6b37-4a3c-9daa-31afe7e2ca23" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DeferredIncomeTaxAssetsNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_6a113c8d-ed83-4a2b-b58f-2619bda6b36a" xlink:to="loc_us-gaap_DeferredIncomeTaxAssetsNet_0aa1438b-6b37-4a3c-9daa-31afe7e2ca23" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLeaseRightOfUseAsset_1d7e244e-7bbe-4999-a1f5-df39dd1412a2" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_OperatingLeaseRightOfUseAsset"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_6a113c8d-ed83-4a2b-b58f-2619bda6b36a" xlink:to="loc_us-gaap_OperatingLeaseRightOfUseAsset_1d7e244e-7bbe-4999-a1f5-df39dd1412a2" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherAssetsNoncurrent_67435c19-375e-405f-971e-567a43388922" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_OtherAssetsNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_6a113c8d-ed83-4a2b-b58f-2619bda6b36a" xlink:to="loc_us-gaap_OtherAssetsNoncurrent_67435c19-375e-405f-971e-567a43388922" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Assets_fcccc6aa-5d53-4a41-bb94-ce63efcf1c4d" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_Assets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_6a113c8d-ed83-4a2b-b58f-2619bda6b36a" xlink:to="loc_us-gaap_Assets_fcccc6aa-5d53-4a41-bb94-ce63efcf1c4d" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_651f3279-8643-4ca0-bbdd-a59834220121" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LiabilitiesAndStockholdersEquityAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_909a7fbc-e7fb-4873-886f-b38180dfcb63" xlink:to="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_651f3279-8643-4ca0-bbdd-a59834220121" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesCurrentAbstract_992a0ed4-a659-4152-92a5-2f951f810ef5" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LiabilitiesCurrentAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_651f3279-8643-4ca0-bbdd-a59834220121" xlink:to="loc_us-gaap_LiabilitiesCurrentAbstract_992a0ed4-a659-4152-92a5-2f951f810ef5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccountsPayableCurrent_e898643b-3147-49e2-90d7-879a46142a34" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AccountsPayableCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesCurrentAbstract_992a0ed4-a659-4152-92a5-2f951f810ef5" xlink:to="loc_us-gaap_AccountsPayableCurrent_e898643b-3147-49e2-90d7-879a46142a34" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccruedLiabilitiesCurrent_9536bde1-eaaf-4d71-98f2-d04296f10d14" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AccruedLiabilitiesCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesCurrentAbstract_992a0ed4-a659-4152-92a5-2f951f810ef5" xlink:to="loc_us-gaap_AccruedLiabilitiesCurrent_9536bde1-eaaf-4d71-98f2-d04296f10d14" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ContractWithCustomerLiabilityCurrent_071fbff0-ead9-49db-b6a8-e9c5bf3400cc" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ContractWithCustomerLiabilityCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesCurrentAbstract_992a0ed4-a659-4152-92a5-2f951f810ef5" xlink:to="loc_us-gaap_ContractWithCustomerLiabilityCurrent_071fbff0-ead9-49db-b6a8-e9c5bf3400cc" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLeaseLiabilityCurrent_4636f889-f30b-4559-ba60-9922c3418188" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_OperatingLeaseLiabilityCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesCurrentAbstract_992a0ed4-a659-4152-92a5-2f951f810ef5" xlink:to="loc_us-gaap_OperatingLeaseLiabilityCurrent_4636f889-f30b-4559-ba60-9922c3418188" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebtCurrent_0e03bc37-8714-4845-a2c5-70c205d4c908" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LongTermDebtCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesCurrentAbstract_992a0ed4-a659-4152-92a5-2f951f810ef5" xlink:to="loc_us-gaap_LongTermDebtCurrent_0e03bc37-8714-4845-a2c5-70c205d4c908" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesCurrent_bb5eac3f-49bc-4192-a452-626344c74762" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LiabilitiesCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesCurrentAbstract_992a0ed4-a659-4152-92a5-2f951f810ef5" xlink:to="loc_us-gaap_LiabilitiesCurrent_bb5eac3f-49bc-4192-a452-626344c74762" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebtNoncurrent_adab8ea0-8f01-430f-b358-359152879186" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LongTermDebtNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_651f3279-8643-4ca0-bbdd-a59834220121" xlink:to="loc_us-gaap_LongTermDebtNoncurrent_adab8ea0-8f01-430f-b358-359152879186" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLeaseLiabilityNoncurrent_fb488146-f4b7-4804-8f82-0dbd80e9015e" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_OperatingLeaseLiabilityNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_651f3279-8643-4ca0-bbdd-a59834220121" xlink:to="loc_us-gaap_OperatingLeaseLiabilityNoncurrent_fb488146-f4b7-4804-8f82-0dbd80e9015e" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccruedIncomeTaxesNoncurrent_94a5071a-cd9f-41f6-8bd0-cde4933faf76" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AccruedIncomeTaxesNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_651f3279-8643-4ca0-bbdd-a59834220121" xlink:to="loc_us-gaap_AccruedIncomeTaxesNoncurrent_94a5071a-cd9f-41f6-8bd0-cde4933faf76" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherLiabilitiesNoncurrent_79c7957e-7de9-446d-b397-f90aa6a502d1" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_OtherLiabilitiesNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_651f3279-8643-4ca0-bbdd-a59834220121" xlink:to="loc_us-gaap_OtherLiabilitiesNoncurrent_79c7957e-7de9-446d-b397-f90aa6a502d1" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Liabilities_574a46e1-4cee-4cbc-818e-147f86ff6172" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_Liabilities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_651f3279-8643-4ca0-bbdd-a59834220121" xlink:to="loc_us-gaap_Liabilities_574a46e1-4cee-4cbc-818e-147f86ff6172" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommitmentsAndContingencies_e4ebe89b-1cde-4509-9af0-902939937949" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CommitmentsAndContingencies"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_909a7fbc-e7fb-4873-886f-b38180dfcb63" xlink:to="loc_us-gaap_CommitmentsAndContingencies_e4ebe89b-1cde-4509-9af0-902939937949" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquityAbstract_faecd7e6-9c8b-43fa-bcc9-e211b1156673" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StockholdersEquityAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_909a7fbc-e7fb-4873-886f-b38180dfcb63" xlink:to="loc_us-gaap_StockholdersEquityAbstract_faecd7e6-9c8b-43fa-bcc9-e211b1156673" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PreferredStockValue_342cbad5-9199-4a75-be21-4d719b326aea" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_PreferredStockValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StockholdersEquityAbstract_faecd7e6-9c8b-43fa-bcc9-e211b1156673" xlink:to="loc_us-gaap_PreferredStockValue_342cbad5-9199-4a75-be21-4d719b326aea" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockValue_c6f2b4dc-9455-4848-b57c-bab4fbd53f4c" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CommonStockValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StockholdersEquityAbstract_faecd7e6-9c8b-43fa-bcc9-e211b1156673" xlink:to="loc_us-gaap_CommonStockValue_c6f2b4dc-9455-4848-b57c-bab4fbd53f4c" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdditionalPaidInCapital_5c3d0fd1-77dd-49c1-babf-3341cc5625f2" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AdditionalPaidInCapital"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StockholdersEquityAbstract_faecd7e6-9c8b-43fa-bcc9-e211b1156673" xlink:to="loc_us-gaap_AdditionalPaidInCapital_5c3d0fd1-77dd-49c1-babf-3341cc5625f2" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetainedEarningsAccumulatedDeficit_a7f2456d-1779-40bf-ab10-c53fd78fa99d" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_RetainedEarningsAccumulatedDeficit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StockholdersEquityAbstract_faecd7e6-9c8b-43fa-bcc9-e211b1156673" xlink:to="loc_us-gaap_RetainedEarningsAccumulatedDeficit_a7f2456d-1779-40bf-ab10-c53fd78fa99d" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquity_33ec2cc5-ed25-484e-a042-1dc9628674ab" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StockholdersEquity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StockholdersEquityAbstract_faecd7e6-9c8b-43fa-bcc9-e211b1156673" xlink:to="loc_us-gaap_StockholdersEquity_33ec2cc5-ed25-484e-a042-1dc9628674ab" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MinorityInterest_8e03fa93-88f2-45b6-99f0-220a13a9fc61" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_MinorityInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StockholdersEquityAbstract_faecd7e6-9c8b-43fa-bcc9-e211b1156673" xlink:to="loc_us-gaap_MinorityInterest_8e03fa93-88f2-45b6-99f0-220a13a9fc61" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest_a6463993-ba19-4ef4-b4e1-1a4d01f3b835" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StockholdersEquityAbstract_faecd7e6-9c8b-43fa-bcc9-e211b1156673" xlink:to="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest_a6463993-ba19-4ef4-b4e1-1a4d01f3b835" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesAndStockholdersEquity_e007179b-e4d5-481a-9e72-797c5d3efece" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LiabilitiesAndStockholdersEquity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_909a7fbc-e7fb-4873-886f-b38180dfcb63" xlink:to="loc_us-gaap_LiabilitiesAndStockholdersEquity_e007179b-e4d5-481a-9e72-797c5d3efece" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementTable_b5aedf4d-cb40-4cf0-bbee-d5f5849e87af" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StatementTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_909a7fbc-e7fb-4873-886f-b38180dfcb63" xlink:to="loc_us-gaap_StatementTable_b5aedf4d-cb40-4cf0-bbee-d5f5849e87af" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementClassOfStockAxis_b4d055dd-ccf4-4cd9-a0c8-08ce1c3b0212" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StatementClassOfStockAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_b5aedf4d-cb40-4cf0-bbee-d5f5849e87af" xlink:to="loc_us-gaap_StatementClassOfStockAxis_b4d055dd-ccf4-4cd9-a0c8-08ce1c3b0212" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_b4d055dd-ccf4-4cd9-a0c8-08ce1c3b0212_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementClassOfStockAxis_b4d055dd-ccf4-4cd9-a0c8-08ce1c3b0212" xlink:to="loc_us-gaap_ClassOfStockDomain_b4d055dd-ccf4-4cd9-a0c8-08ce1c3b0212_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_edf8c2e1-68cd-44f4-8bea-b2e4dc30e876" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementClassOfStockAxis_b4d055dd-ccf4-4cd9-a0c8-08ce1c3b0212" xlink:to="loc_us-gaap_ClassOfStockDomain_edf8c2e1-68cd-44f4-8bea-b2e4dc30e876" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonClassAMember_514a8bcb-4304-4438-9018-854c7e19c631" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CommonClassAMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_edf8c2e1-68cd-44f4-8bea-b2e4dc30e876" xlink:to="loc_us-gaap_CommonClassAMember_514a8bcb-4304-4438-9018-854c7e19c631" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonClassBMember_96f2ff67-21e4-4c1f-83fc-a97ef2afa905" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CommonClassBMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_edf8c2e1-68cd-44f4-8bea-b2e4dc30e876" xlink:to="loc_us-gaap_CommonClassBMember_96f2ff67-21e4-4c1f-83fc-a97ef2afa905" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonClassCMember_3a45b87b-0be1-4c83-bbb1-92b6989d1f0e" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CommonClassCMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_edf8c2e1-68cd-44f4-8bea-b2e4dc30e876" xlink:to="loc_us-gaap_CommonClassCMember_3a45b87b-0be1-4c83-bbb1-92b6989d1f0e" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_brlt_CommonClassDMember_21b06335-2dc3-440a-bd1a-1a6d9965fa46" xlink:href="brlt-20230331.xsd#brlt_CommonClassDMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_edf8c2e1-68cd-44f4-8bea-b2e4dc30e876" xlink:to="loc_brlt_CommonClassDMember_21b06335-2dc3-440a-bd1a-1a6d9965fa46" xlink:type="arc" order="3"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://brilliantearth.com/role/UNAUDITEDCONDENSEDCONSOLIDATEDBALANCESHEETSParenthetical" xlink:type="simple" xlink:href="brlt-20230331.xsd#UNAUDITEDCONDENSEDCONSOLIDATEDBALANCESHEETSParenthetical"/>
  <link:definitionLink xlink:role="http://brilliantearth.com/role/UNAUDITEDCONDENSEDCONSOLIDATEDBALANCESHEETSParenthetical" xlink:type="extended" id="i148af98abfb94125b8dddce4f8f622ce_UNAUDITEDCONDENSEDCONSOLIDATEDBALANCESHEETSParenthetical">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_7af9617e-89cf-4451-903e-a1c20449ffab" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StatementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PreferredStockParOrStatedValuePerShare_211c69e4-2b6b-46c3-9291-945b45447d5b" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_PreferredStockParOrStatedValuePerShare"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_7af9617e-89cf-4451-903e-a1c20449ffab" xlink:to="loc_us-gaap_PreferredStockParOrStatedValuePerShare_211c69e4-2b6b-46c3-9291-945b45447d5b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PreferredStockSharesAuthorized_faaabbab-eaa6-4a62-8df9-b00bc2136936" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_PreferredStockSharesAuthorized"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_7af9617e-89cf-4451-903e-a1c20449ffab" xlink:to="loc_us-gaap_PreferredStockSharesAuthorized_faaabbab-eaa6-4a62-8df9-b00bc2136936" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PreferredStockSharesIssued_61166368-4867-449f-b5b2-0dca7dd3a087" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_PreferredStockSharesIssued"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_7af9617e-89cf-4451-903e-a1c20449ffab" xlink:to="loc_us-gaap_PreferredStockSharesIssued_61166368-4867-449f-b5b2-0dca7dd3a087" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PreferredStockSharesOutstanding_eb844bdd-7d01-4a38-986b-7d3639c90e3c" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_PreferredStockSharesOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_7af9617e-89cf-4451-903e-a1c20449ffab" xlink:to="loc_us-gaap_PreferredStockSharesOutstanding_eb844bdd-7d01-4a38-986b-7d3639c90e3c" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockParOrStatedValuePerShare_1b1432b3-df82-4d3d-b65e-53a5db5ce3d6" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CommonStockParOrStatedValuePerShare"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_7af9617e-89cf-4451-903e-a1c20449ffab" xlink:to="loc_us-gaap_CommonStockParOrStatedValuePerShare_1b1432b3-df82-4d3d-b65e-53a5db5ce3d6" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesAuthorized_1f835f32-e081-4771-bc36-0944b35fcdb7" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CommonStockSharesAuthorized"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_7af9617e-89cf-4451-903e-a1c20449ffab" xlink:to="loc_us-gaap_CommonStockSharesAuthorized_1f835f32-e081-4771-bc36-0944b35fcdb7" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesIssued_e4dbf329-d0f7-4395-9d08-37d8aa48052b" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CommonStockSharesIssued"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_7af9617e-89cf-4451-903e-a1c20449ffab" xlink:to="loc_us-gaap_CommonStockSharesIssued_e4dbf329-d0f7-4395-9d08-37d8aa48052b" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesOutstanding_bdf76a25-1979-43fd-bea8-fa0d695d4b34" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CommonStockSharesOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_7af9617e-89cf-4451-903e-a1c20449ffab" xlink:to="loc_us-gaap_CommonStockSharesOutstanding_bdf76a25-1979-43fd-bea8-fa0d695d4b34" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementTable_be9f47fa-3473-4f6d-b231-adee98173972" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StatementTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_7af9617e-89cf-4451-903e-a1c20449ffab" xlink:to="loc_us-gaap_StatementTable_be9f47fa-3473-4f6d-b231-adee98173972" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementClassOfStockAxis_f8760397-f3e3-49f0-9e79-5c6d7f3f31f5" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StatementClassOfStockAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_be9f47fa-3473-4f6d-b231-adee98173972" xlink:to="loc_us-gaap_StatementClassOfStockAxis_f8760397-f3e3-49f0-9e79-5c6d7f3f31f5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_f8760397-f3e3-49f0-9e79-5c6d7f3f31f5_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementClassOfStockAxis_f8760397-f3e3-49f0-9e79-5c6d7f3f31f5" xlink:to="loc_us-gaap_ClassOfStockDomain_f8760397-f3e3-49f0-9e79-5c6d7f3f31f5_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_f55fe054-cb8a-42fa-8e60-277241ea9482" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementClassOfStockAxis_f8760397-f3e3-49f0-9e79-5c6d7f3f31f5" xlink:to="loc_us-gaap_ClassOfStockDomain_f55fe054-cb8a-42fa-8e60-277241ea9482" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonClassAMember_62cecf84-8a5e-4931-9d01-08e7313cf916" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CommonClassAMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_f55fe054-cb8a-42fa-8e60-277241ea9482" xlink:to="loc_us-gaap_CommonClassAMember_62cecf84-8a5e-4931-9d01-08e7313cf916" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonClassBMember_62184cc7-d218-4a2f-8069-edb5fef1b166" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CommonClassBMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_f55fe054-cb8a-42fa-8e60-277241ea9482" xlink:to="loc_us-gaap_CommonClassBMember_62184cc7-d218-4a2f-8069-edb5fef1b166" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonClassCMember_64574314-f858-485e-8ea2-33ab6dad19fc" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CommonClassCMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_f55fe054-cb8a-42fa-8e60-277241ea9482" xlink:to="loc_us-gaap_CommonClassCMember_64574314-f858-485e-8ea2-33ab6dad19fc" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_brlt_CommonClassDMember_1cca3c67-08f4-49c0-8238-cbf05ae9d4e8" xlink:href="brlt-20230331.xsd#brlt_CommonClassDMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_f55fe054-cb8a-42fa-8e60-277241ea9482" xlink:to="loc_brlt_CommonClassDMember_1cca3c67-08f4-49c0-8238-cbf05ae9d4e8" xlink:type="arc" order="3"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://brilliantearth.com/role/UNAUDITEDCONDENSEDCONSOLIDATEDSTATEMENTSOFCHANGESINEQUITY" xlink:type="simple" xlink:href="brlt-20230331.xsd#UNAUDITEDCONDENSEDCONSOLIDATEDSTATEMENTSOFCHANGESINEQUITY"/>
  <link:definitionLink xlink:role="http://brilliantearth.com/role/UNAUDITEDCONDENSEDCONSOLIDATEDSTATEMENTSOFCHANGESINEQUITY" xlink:type="extended" id="ifed858d30fb5494382fb93b105efd5da_UNAUDITEDCONDENSEDCONSOLIDATEDSTATEMENTSOFCHANGESINEQUITY">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_a814322e-186d-47c9-b27b-ed34695dcaa0" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StatementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_fa2181df-5fad-467a-b6e2-81d950c0b187" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_IncreaseDecreaseInStockholdersEquityRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_a814322e-186d-47c9-b27b-ed34695dcaa0" xlink:to="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_fa2181df-5fad-467a-b6e2-81d950c0b187" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesOutstanding_739cbd30-4186-4871-9ffd-733f3722902d" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CommonStockSharesOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_fa2181df-5fad-467a-b6e2-81d950c0b187" xlink:to="loc_us-gaap_CommonStockSharesOutstanding_739cbd30-4186-4871-9ffd-733f3722902d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest_02452cfb-742d-4a96-ae42-5361f03ac391" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_fa2181df-5fad-467a-b6e2-81d950c0b187" xlink:to="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest_02452cfb-742d-4a96-ae42-5361f03ac391" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonUnitOutstanding_e1f2fcea-4622-4a4e-a4aa-d0a4ecc7f339" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CommonUnitOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_fa2181df-5fad-467a-b6e2-81d950c0b187" xlink:to="loc_us-gaap_CommonUnitOutstanding_e1f2fcea-4622-4a4e-a4aa-d0a4ecc7f339" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MembersEquity_3ecc5da9-6cf7-4b5f-8200-116d67b571fa" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_MembersEquity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_fa2181df-5fad-467a-b6e2-81d950c0b187" xlink:to="loc_us-gaap_MembersEquity_3ecc5da9-6cf7-4b5f-8200-116d67b571fa" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_brlt_LimitedLiabilityCompanyLLCMembersEquityTaxDistributionsToMembers_8c30b5e9-381b-4bf0-b6b8-0f12e88125f5" xlink:href="brlt-20230331.xsd#brlt_LimitedLiabilityCompanyLLCMembersEquityTaxDistributionsToMembers"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_fa2181df-5fad-467a-b6e2-81d950c0b187" xlink:to="loc_brlt_LimitedLiabilityCompanyLLCMembersEquityTaxDistributionsToMembers_8c30b5e9-381b-4bf0-b6b8-0f12e88125f5" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodSharesConversionOfConvertibleSecurities_89940646-93b1-4a2c-bbc8-1d0f91ed5d63" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StockIssuedDuringPeriodSharesConversionOfConvertibleSecurities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_fa2181df-5fad-467a-b6e2-81d950c0b187" xlink:to="loc_us-gaap_StockIssuedDuringPeriodSharesConversionOfConvertibleSecurities_89940646-93b1-4a2c-bbc8-1d0f91ed5d63" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodSharesRestrictedStockAwardNetOfForfeitures_a7ade3f5-0a9e-4d9c-be89-1b90add47ede" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StockIssuedDuringPeriodSharesRestrictedStockAwardNetOfForfeitures"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_fa2181df-5fad-467a-b6e2-81d950c0b187" xlink:to="loc_us-gaap_StockIssuedDuringPeriodSharesRestrictedStockAwardNetOfForfeitures_a7ade3f5-0a9e-4d9c-be89-1b90add47ede" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodSharesShareBasedCompensationGross_bfbafa60-0140-404e-97bd-e38445ea1dd9" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StockIssuedDuringPeriodSharesShareBasedCompensationGross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_fa2181df-5fad-467a-b6e2-81d950c0b187" xlink:to="loc_us-gaap_StockIssuedDuringPeriodSharesShareBasedCompensationGross_bfbafa60-0140-404e-97bd-e38445ea1dd9" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_brlt_AdjustmentsToAdditionalPaidInCapitalDeferredTaxAdjustment_62f278d6-d647-4f37-afc1-b29cea2e0e5f" xlink:href="brlt-20230331.xsd#brlt_AdjustmentsToAdditionalPaidInCapitalDeferredTaxAdjustment"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_fa2181df-5fad-467a-b6e2-81d950c0b187" xlink:to="loc_brlt_AdjustmentsToAdditionalPaidInCapitalDeferredTaxAdjustment_62f278d6-d647-4f37-afc1-b29cea2e0e5f" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue_648607e5-8631-4e10-a922-24f997c0abe3" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_fa2181df-5fad-467a-b6e2-81d950c0b187" xlink:to="loc_us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue_648607e5-8631-4e10-a922-24f997c0abe3" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProfitLoss_e1837eb5-dc65-4225-9868-13a36aab8c34" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ProfitLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_fa2181df-5fad-467a-b6e2-81d950c0b187" xlink:to="loc_us-gaap_ProfitLoss_e1837eb5-dc65-4225-9868-13a36aab8c34" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MinorityInterestDecreaseFromRedemptions_ac1a0aa6-c5d3-439f-924a-f453778142bc" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_MinorityInterestDecreaseFromRedemptions"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_fa2181df-5fad-467a-b6e2-81d950c0b187" xlink:to="loc_us-gaap_MinorityInterestDecreaseFromRedemptions_ac1a0aa6-c5d3-439f-924a-f453778142bc" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesOutstanding_d4bf709a-9f36-4d9b-b2cd-23a28e426df4" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CommonStockSharesOutstanding"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest_c00aa51d-73b3-409c-b0c1-debc695a5819" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonUnitOutstanding_a3ec557e-02a2-4f88-8f32-3da4d467cee6" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CommonUnitOutstanding"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MembersEquity_8852802c-4e5b-4d3c-a5d1-d449e2f06698" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_MembersEquity"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementTable_506515f7-f252-4da1-b7c5-1a8b6d6a1e96" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StatementTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_a814322e-186d-47c9-b27b-ed34695dcaa0" xlink:to="loc_us-gaap_StatementTable_506515f7-f252-4da1-b7c5-1a8b6d6a1e96" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementClassOfStockAxis_70c63f15-66e3-4cf7-9805-e6d647998200" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StatementClassOfStockAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_506515f7-f252-4da1-b7c5-1a8b6d6a1e96" xlink:to="loc_us-gaap_StatementClassOfStockAxis_70c63f15-66e3-4cf7-9805-e6d647998200" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_70c63f15-66e3-4cf7-9805-e6d647998200_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementClassOfStockAxis_70c63f15-66e3-4cf7-9805-e6d647998200" xlink:to="loc_us-gaap_ClassOfStockDomain_70c63f15-66e3-4cf7-9805-e6d647998200_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_598085a3-59de-4d3f-805c-f61ff26076d6" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementClassOfStockAxis_70c63f15-66e3-4cf7-9805-e6d647998200" xlink:to="loc_us-gaap_ClassOfStockDomain_598085a3-59de-4d3f-805c-f61ff26076d6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonClassAMember_fa27700a-cf49-41bf-aed5-5cdd03c611e2" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CommonClassAMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_598085a3-59de-4d3f-805c-f61ff26076d6" xlink:to="loc_us-gaap_CommonClassAMember_fa27700a-cf49-41bf-aed5-5cdd03c611e2" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonClassBMember_903734c2-8473-4f71-8b26-8b5c225ee425" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CommonClassBMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_598085a3-59de-4d3f-805c-f61ff26076d6" xlink:to="loc_us-gaap_CommonClassBMember_903734c2-8473-4f71-8b26-8b5c225ee425" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonClassCMember_32faef36-c44c-43ce-a1e6-5be47cf5de7a" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CommonClassCMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_598085a3-59de-4d3f-805c-f61ff26076d6" xlink:to="loc_us-gaap_CommonClassCMember_32faef36-c44c-43ce-a1e6-5be47cf5de7a" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementEquityComponentsAxis_6021a118-28ad-4a84-9d7c-5a2b2e7dee6a" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StatementEquityComponentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_506515f7-f252-4da1-b7c5-1a8b6d6a1e96" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_6021a118-28ad-4a84-9d7c-5a2b2e7dee6a" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_6021a118-28ad-4a84-9d7c-5a2b2e7dee6a_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_6021a118-28ad-4a84-9d7c-5a2b2e7dee6a" xlink:to="loc_us-gaap_EquityComponentDomain_6021a118-28ad-4a84-9d7c-5a2b2e7dee6a_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_d42f2f7f-660a-4bfc-ae12-e66409f89ac1" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_6021a118-28ad-4a84-9d7c-5a2b2e7dee6a" xlink:to="loc_us-gaap_EquityComponentDomain_d42f2f7f-660a-4bfc-ae12-e66409f89ac1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockMember_ae5d8b6d-c353-41b1-8634-fca77ecf4d3c" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CommonStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_d42f2f7f-660a-4bfc-ae12-e66409f89ac1" xlink:to="loc_us-gaap_CommonStockMember_ae5d8b6d-c353-41b1-8634-fca77ecf4d3c" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdditionalPaidInCapitalMember_a3389f21-1169-48d5-bf85-47c0287dc95f" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AdditionalPaidInCapitalMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_d42f2f7f-660a-4bfc-ae12-e66409f89ac1" xlink:to="loc_us-gaap_AdditionalPaidInCapitalMember_a3389f21-1169-48d5-bf85-47c0287dc95f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetainedEarningsMember_b59a7903-4e71-4fd1-944d-eee7306ea1b7" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_RetainedEarningsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_d42f2f7f-660a-4bfc-ae12-e66409f89ac1" xlink:to="loc_us-gaap_RetainedEarningsMember_b59a7903-4e71-4fd1-944d-eee7306ea1b7" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ParentMember_86284cc1-5b89-40ce-acde-032db4b2a537" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ParentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_d42f2f7f-660a-4bfc-ae12-e66409f89ac1" xlink:to="loc_us-gaap_ParentMember_86284cc1-5b89-40ce-acde-032db4b2a537" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NoncontrollingInterestMember_08b460b4-385e-4903-9014-18cf35b1aa65" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_NoncontrollingInterestMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_d42f2f7f-660a-4bfc-ae12-e66409f89ac1" xlink:to="loc_us-gaap_NoncontrollingInterestMember_08b460b4-385e-4903-9014-18cf35b1aa65" xlink:type="arc" order="4"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://brilliantearth.com/role/DescriptionofBusinessandSummaryofSignificantAccountingPoliciesDetails" xlink:type="simple" xlink:href="brlt-20230331.xsd#DescriptionofBusinessandSummaryofSignificantAccountingPoliciesDetails"/>
  <link:definitionLink xlink:role="http://brilliantearth.com/role/DescriptionofBusinessandSummaryofSignificantAccountingPoliciesDetails" xlink:type="extended" id="id3fe1043e7df43b1af3809dc13e65981_DescriptionofBusinessandSummaryofSignificantAccountingPoliciesDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MinorityInterestLineItems_65abc804-3ed4-4aad-b727-361f35061425" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_MinorityInterestLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_brlt_NumberOfShowrooms_9365a542-5ad0-468f-92d6-18795a9debb4" xlink:href="brlt-20230331.xsd#brlt_NumberOfShowrooms"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MinorityInterestLineItems_65abc804-3ed4-4aad-b727-361f35061425" xlink:to="loc_brlt_NumberOfShowrooms_9365a542-5ad0-468f-92d6-18795a9debb4" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MinorityInterestOwnershipPercentageByParent_c8543fd1-b12e-4fc0-9ed4-ae160ee3cb52" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_MinorityInterestOwnershipPercentageByParent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MinorityInterestLineItems_65abc804-3ed4-4aad-b727-361f35061425" xlink:to="loc_us-gaap_MinorityInterestOwnershipPercentageByParent_c8543fd1-b12e-4fc0-9ed4-ae160ee3cb52" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MinorityInterestTable_5337f414-ef0a-4864-890f-4a34c9fcf49e" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_MinorityInterestTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_MinorityInterestLineItems_65abc804-3ed4-4aad-b727-361f35061425" xlink:to="loc_us-gaap_MinorityInterestTable_5337f414-ef0a-4864-890f-4a34c9fcf49e" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_OwnershipAxis_808d97b6-294e-4bff-99c0-10b32056b524" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_OwnershipAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_MinorityInterestTable_5337f414-ef0a-4864-890f-4a34c9fcf49e" xlink:to="loc_srt_OwnershipAxis_808d97b6-294e-4bff-99c0-10b32056b524" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_OwnershipDomain_808d97b6-294e-4bff-99c0-10b32056b524_default" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_OwnershipDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_OwnershipAxis_808d97b6-294e-4bff-99c0-10b32056b524" xlink:to="loc_srt_OwnershipDomain_808d97b6-294e-4bff-99c0-10b32056b524_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_OwnershipDomain_376103d4-2fad-4e0f-90f8-25d15b740fd9" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_OwnershipDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_OwnershipAxis_808d97b6-294e-4bff-99c0-10b32056b524" xlink:to="loc_srt_OwnershipDomain_376103d4-2fad-4e0f-90f8-25d15b740fd9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_brlt_BrilliantEarthLLCMember_3741a18e-c150-4d2e-981f-00767dbc79ea" xlink:href="brlt-20230331.xsd#brlt_BrilliantEarthLLCMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_OwnershipDomain_376103d4-2fad-4e0f-90f8-25d15b740fd9" xlink:to="loc_brlt_BrilliantEarthLLCMember_3741a18e-c150-4d2e-981f-00767dbc79ea" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://brilliantearth.com/role/EarningsPerShareDetails" xlink:type="simple" xlink:href="brlt-20230331.xsd#EarningsPerShareDetails"/>
  <link:definitionLink xlink:role="http://brilliantearth.com/role/EarningsPerShareDetails" xlink:type="extended" id="if5f1223afaa345ed8e7a289206cf0a38_EarningsPerShareDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_be844849-04a9-4d4f-8d58-d0b8846263ae" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLoss_9794a48e-1235-499e-90e4-5ae7e4d2e1fa" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_NetIncomeLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_be844849-04a9-4d4f-8d58-d0b8846263ae" xlink:to="loc_us-gaap_NetIncomeLoss_9794a48e-1235-499e-90e4-5ae7e4d2e1fa" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_brlt_NetIncomeLossFromImpactOfAssumedRedemptionOfAllLLCUnitsToCommonStock_c623b47a-7819-406f-bf66-889a11eefdb6" xlink:href="brlt-20230331.xsd#brlt_NetIncomeLossFromImpactOfAssumedRedemptionOfAllLLCUnitsToCommonStock"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_be844849-04a9-4d4f-8d58-d0b8846263ae" xlink:to="loc_brlt_NetIncomeLossFromImpactOfAssumedRedemptionOfAllLLCUnitsToCommonStock_c623b47a-7819-406f-bf66-889a11eefdb6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_brlt_IncomeTaxExpenseBenefitPortionAttributableToNoncontrollingInterest_61d83bc6-9fab-4783-97e1-93a804a8c160" xlink:href="brlt-20230331.xsd#brlt_IncomeTaxExpenseBenefitPortionAttributableToNoncontrollingInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_be844849-04a9-4d4f-8d58-d0b8846263ae" xlink:to="loc_brlt_IncomeTaxExpenseBenefitPortionAttributableToNoncontrollingInterest_61d83bc6-9fab-4783-97e1-93a804a8c160" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLossAvailableToCommonStockholdersDiluted_8cd00184-07d7-4c67-bac3-05158fba8441" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_NetIncomeLossAvailableToCommonStockholdersDiluted"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_be844849-04a9-4d4f-8d58-d0b8846263ae" xlink:to="loc_us-gaap_NetIncomeLossAvailableToCommonStockholdersDiluted_8cd00184-07d7-4c67-bac3-05158fba8441" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingBasic_cf14769f-5973-4ea6-8ecc-a2ab8c3d0a1e" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_WeightedAverageNumberOfSharesOutstandingBasic"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_be844849-04a9-4d4f-8d58-d0b8846263ae" xlink:to="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingBasic_cf14769f-5973-4ea6-8ecc-a2ab8c3d0a1e" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_WeightedAverageNumberDilutedSharesOutstandingAdjustment_d71c8897-58dc-4331-8ea0-dd8c21a262b4" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_WeightedAverageNumberDilutedSharesOutstandingAdjustment"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_be844849-04a9-4d4f-8d58-d0b8846263ae" xlink:to="loc_us-gaap_WeightedAverageNumberDilutedSharesOutstandingAdjustment_d71c8897-58dc-4331-8ea0-dd8c21a262b4" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding_464fb84a-97dc-47cf-92bf-74aa3cb6541e" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_be844849-04a9-4d4f-8d58-d0b8846263ae" xlink:to="loc_us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding_464fb84a-97dc-47cf-92bf-74aa3cb6541e" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EarningsPerShareBasic_4f77f36f-d2ee-4317-9df6-8d79ccf7e244" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_EarningsPerShareBasic"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_be844849-04a9-4d4f-8d58-d0b8846263ae" xlink:to="loc_us-gaap_EarningsPerShareBasic_4f77f36f-d2ee-4317-9df6-8d79ccf7e244" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EarningsPerShareDiluted_57a3e8a4-2b7f-4aa2-82ca-ce2290b6315c" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_EarningsPerShareDiluted"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_be844849-04a9-4d4f-8d58-d0b8846263ae" xlink:to="loc_us-gaap_EarningsPerShareDiluted_57a3e8a4-2b7f-4aa2-82ca-ce2290b6315c" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount_2e6f12b4-569e-4aa1-aecd-0e43e1a6bcef" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_be844849-04a9-4d4f-8d58-d0b8846263ae" xlink:to="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount_2e6f12b4-569e-4aa1-aecd-0e43e1a6bcef" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable_5b4cd3b0-7fdc-4c3c-a089-c8229d105343" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_be844849-04a9-4d4f-8d58-d0b8846263ae" xlink:to="loc_us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable_5b4cd3b0-7fdc-4c3c-a089-c8229d105343" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis_4daa680a-4d7d-4955-b612-28a986b9bbcc" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable_5b4cd3b0-7fdc-4c3c-a089-c8229d105343" xlink:to="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis_4daa680a-4d7d-4955-b612-28a986b9bbcc" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AntidilutiveSecuritiesNameDomain_4daa680a-4d7d-4955-b612-28a986b9bbcc_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AntidilutiveSecuritiesNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis_4daa680a-4d7d-4955-b612-28a986b9bbcc" xlink:to="loc_us-gaap_AntidilutiveSecuritiesNameDomain_4daa680a-4d7d-4955-b612-28a986b9bbcc_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AntidilutiveSecuritiesNameDomain_7bd68eea-e11e-4633-b857-c2a360f9e379" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AntidilutiveSecuritiesNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis_4daa680a-4d7d-4955-b612-28a986b9bbcc" xlink:to="loc_us-gaap_AntidilutiveSecuritiesNameDomain_7bd68eea-e11e-4633-b857-c2a360f9e379" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_brlt_VestedLLCUnitsExchangeableForCommonStockMember_39043e2a-2647-43f1-aa1c-a36abfaf72c9" xlink:href="brlt-20230331.xsd#brlt_VestedLLCUnitsExchangeableForCommonStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesNameDomain_7bd68eea-e11e-4633-b857-c2a360f9e379" xlink:to="loc_brlt_VestedLLCUnitsExchangeableForCommonStockMember_39043e2a-2647-43f1-aa1c-a36abfaf72c9" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_brlt_UnvestedLLCUnitsExchangeableForCommonStockMember_192821be-092b-4e7d-b1e9-73a5bee9f6e6" xlink:href="brlt-20230331.xsd#brlt_UnvestedLLCUnitsExchangeableForCommonStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesNameDomain_7bd68eea-e11e-4633-b857-c2a360f9e379" xlink:to="loc_brlt_UnvestedLLCUnitsExchangeableForCommonStockMember_192821be-092b-4e7d-b1e9-73a5bee9f6e6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_brlt_RestrictedStockUnitsRSUsAndEmployeeOptionsMember_682b3d45-21ff-4375-aac5-ddf7925f6d57" xlink:href="brlt-20230331.xsd#brlt_RestrictedStockUnitsRSUsAndEmployeeOptionsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesNameDomain_7bd68eea-e11e-4633-b857-c2a360f9e379" xlink:to="loc_brlt_RestrictedStockUnitsRSUsAndEmployeeOptionsMember_682b3d45-21ff-4375-aac5-ddf7925f6d57" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedStockUnitsRSUMember_451e0960-ec05-4884-80b0-753b208c0165" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_RestrictedStockUnitsRSUMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_brlt_RestrictedStockUnitsRSUsAndEmployeeOptionsMember_682b3d45-21ff-4375-aac5-ddf7925f6d57" xlink:to="loc_us-gaap_RestrictedStockUnitsRSUMember_451e0960-ec05-4884-80b0-753b208c0165" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeStockOptionMember_14c14fae-7bbc-4d8d-aa61-b1111e273f9d" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_EmployeeStockOptionMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_brlt_RestrictedStockUnitsRSUsAndEmployeeOptionsMember_682b3d45-21ff-4375-aac5-ddf7925f6d57" xlink:to="loc_us-gaap_EmployeeStockOptionMember_14c14fae-7bbc-4d8d-aa61-b1111e273f9d" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://brilliantearth.com/role/RevenuefromContractwithCustomerScheduleofDisaggregationofRevenueDetails" xlink:type="simple" xlink:href="brlt-20230331.xsd#RevenuefromContractwithCustomerScheduleofDisaggregationofRevenueDetails"/>
  <link:definitionLink xlink:role="http://brilliantearth.com/role/RevenuefromContractwithCustomerScheduleofDisaggregationofRevenueDetails" xlink:type="extended" id="ie2786758501c49a58524437156e07e40_RevenuefromContractwithCustomerScheduleofDisaggregationofRevenueDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisaggregationOfRevenueLineItems_56ca10db-07de-4339-a411-8fa310db1370" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DisaggregationOfRevenueLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_15556f60-b4f8-46a6-919a-6f6f9c597548" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_56ca10db-07de-4339-a411-8fa310db1370" xlink:to="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_15556f60-b4f8-46a6-919a-6f6f9c597548" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisaggregationOfRevenueTable_ef044a52-7abc-47d9-b492-556084fc5001" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DisaggregationOfRevenueTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_56ca10db-07de-4339-a411-8fa310db1370" xlink:to="loc_us-gaap_DisaggregationOfRevenueTable_ef044a52-7abc-47d9-b492-556084fc5001" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_StatementGeographicalAxis_11caa01a-6f29-4a25-be1a-0e40a9fe2c6e" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_StatementGeographicalAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DisaggregationOfRevenueTable_ef044a52-7abc-47d9-b492-556084fc5001" xlink:to="loc_srt_StatementGeographicalAxis_11caa01a-6f29-4a25-be1a-0e40a9fe2c6e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_SegmentGeographicalDomain_11caa01a-6f29-4a25-be1a-0e40a9fe2c6e_default" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_SegmentGeographicalDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_StatementGeographicalAxis_11caa01a-6f29-4a25-be1a-0e40a9fe2c6e" xlink:to="loc_srt_SegmentGeographicalDomain_11caa01a-6f29-4a25-be1a-0e40a9fe2c6e_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_SegmentGeographicalDomain_73db9ded-f1f4-434c-a752-d07ed94e3e21" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_SegmentGeographicalDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_StatementGeographicalAxis_11caa01a-6f29-4a25-be1a-0e40a9fe2c6e" xlink:to="loc_srt_SegmentGeographicalDomain_73db9ded-f1f4-434c-a752-d07ed94e3e21" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_country_US_1f01363d-48ea-4e65-bb4b-21cfae55ec0e" xlink:href="https://xbrl.sec.gov/country/2022/country-2022.xsd#country_US"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_73db9ded-f1f4-434c-a752-d07ed94e3e21" xlink:to="loc_country_US_1f01363d-48ea-4e65-bb4b-21cfae55ec0e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NonUsMember_b3ef56f1-c245-4964-9822-3ec36e12531d" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_NonUsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_73db9ded-f1f4-434c-a752-d07ed94e3e21" xlink:to="loc_us-gaap_NonUsMember_b3ef56f1-c245-4964-9822-3ec36e12531d" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://brilliantearth.com/role/InventoriesNetScheduleofInventoriesNetDetails" xlink:type="simple" xlink:href="brlt-20230331.xsd#InventoriesNetScheduleofInventoriesNetDetails"/>
  <link:definitionLink xlink:role="http://brilliantearth.com/role/InventoriesNetScheduleofInventoriesNetDetails" xlink:type="extended" id="i6a36b4cb44d345338ece72819e7af88c_InventoriesNetScheduleofInventoriesNetDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InventoryLineItems_61b22c35-6a8b-4b64-bd19-e5644d0a8d63" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_InventoryLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InventoryGross_172aa5bc-5ad8-4990-a9f9-92d89f069557" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_InventoryGross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InventoryLineItems_61b22c35-6a8b-4b64-bd19-e5644d0a8d63" xlink:to="loc_us-gaap_InventoryGross_172aa5bc-5ad8-4990-a9f9-92d89f069557" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InventoryValuationReserves_7cc04ac2-aace-4f9d-916b-39b0d2116b45" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_InventoryValuationReserves"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InventoryLineItems_61b22c35-6a8b-4b64-bd19-e5644d0a8d63" xlink:to="loc_us-gaap_InventoryValuationReserves_7cc04ac2-aace-4f9d-916b-39b0d2116b45" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InventoryNet_ad2fa3fd-369f-4d6e-b000-b48808924115" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_InventoryNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InventoryLineItems_61b22c35-6a8b-4b64-bd19-e5644d0a8d63" xlink:to="loc_us-gaap_InventoryNet_ad2fa3fd-369f-4d6e-b000-b48808924115" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InventoryCurrentTable_0c2c8ffd-978a-4e41-8885-3b2157f9c934" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_InventoryCurrentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_InventoryLineItems_61b22c35-6a8b-4b64-bd19-e5644d0a8d63" xlink:to="loc_us-gaap_InventoryCurrentTable_0c2c8ffd-978a-4e41-8885-3b2157f9c934" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PublicUtilitiesInventoryAxis_46b7dca9-1872-4fec-b510-62ffbb95cc9f" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_PublicUtilitiesInventoryAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_InventoryCurrentTable_0c2c8ffd-978a-4e41-8885-3b2157f9c934" xlink:to="loc_us-gaap_PublicUtilitiesInventoryAxis_46b7dca9-1872-4fec-b510-62ffbb95cc9f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PublicUtilitiesInventoryTypeDomain_46b7dca9-1872-4fec-b510-62ffbb95cc9f_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_PublicUtilitiesInventoryTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PublicUtilitiesInventoryAxis_46b7dca9-1872-4fec-b510-62ffbb95cc9f" xlink:to="loc_us-gaap_PublicUtilitiesInventoryTypeDomain_46b7dca9-1872-4fec-b510-62ffbb95cc9f_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PublicUtilitiesInventoryTypeDomain_ae763ba2-add4-449b-9f58-b65714c78b8f" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_PublicUtilitiesInventoryTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PublicUtilitiesInventoryAxis_46b7dca9-1872-4fec-b510-62ffbb95cc9f" xlink:to="loc_us-gaap_PublicUtilitiesInventoryTypeDomain_ae763ba2-add4-449b-9f58-b65714c78b8f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_brlt_LooseDiamondsMember_304e5009-a0fa-461d-8f1d-859968a68e3d" xlink:href="brlt-20230331.xsd#brlt_LooseDiamondsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PublicUtilitiesInventoryTypeDomain_ae763ba2-add4-449b-9f58-b65714c78b8f" xlink:to="loc_brlt_LooseDiamondsMember_304e5009-a0fa-461d-8f1d-859968a68e3d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_brlt_FineJewelryAndOtherMember_d050f92d-380e-4ea5-8501-7bf6ef514447" xlink:href="brlt-20230331.xsd#brlt_FineJewelryAndOtherMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PublicUtilitiesInventoryTypeDomain_ae763ba2-add4-449b-9f58-b65714c78b8f" xlink:to="loc_brlt_FineJewelryAndOtherMember_d050f92d-380e-4ea5-8501-7bf6ef514447" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://brilliantearth.com/role/LeasesNarrativeDetails" xlink:type="simple" xlink:href="brlt-20230331.xsd#LeasesNarrativeDetails"/>
  <link:definitionLink xlink:role="http://brilliantearth.com/role/LeasesNarrativeDetails" xlink:type="extended" id="i8c9feb7b0ac24891b51795854c2830ec_LeasesNarrativeDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LesseeLeaseDescriptionLineItems_3599018e-8304-445f-ad24-a6f68a99d522" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LesseeLeaseDescriptionLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LesseeOperatingLeaseTermOfContract_d284692e-6404-4ea7-9c9c-5b8c0c62f4c3" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LesseeOperatingLeaseTermOfContract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LesseeLeaseDescriptionLineItems_3599018e-8304-445f-ad24-a6f68a99d522" xlink:to="loc_us-gaap_LesseeOperatingLeaseTermOfContract_d284692e-6404-4ea7-9c9c-5b8c0c62f4c3" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_brlt_LesseeOperatingLeaseLeaseNotYetCommencedAmount_0f19a650-1c24-493c-98b2-662d449348ca" xlink:href="brlt-20230331.xsd#brlt_LesseeOperatingLeaseLeaseNotYetCommencedAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LesseeLeaseDescriptionLineItems_3599018e-8304-445f-ad24-a6f68a99d522" xlink:to="loc_brlt_LesseeOperatingLeaseLeaseNotYetCommencedAmount_0f19a650-1c24-493c-98b2-662d449348ca" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LesseeOperatingLeaseLeaseNotYetCommencedTermOfContract1_4697a542-4113-48f7-aad3-dd0b42f186d2" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LesseeOperatingLeaseLeaseNotYetCommencedTermOfContract1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LesseeLeaseDescriptionLineItems_3599018e-8304-445f-ad24-a6f68a99d522" xlink:to="loc_us-gaap_LesseeOperatingLeaseLeaseNotYetCommencedTermOfContract1_4697a542-4113-48f7-aad3-dd0b42f186d2" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LesseeLeaseDescriptionTable_e2a7b6e7-f6b7-4ab4-8109-76af39420c06" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LesseeLeaseDescriptionTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_LesseeLeaseDescriptionLineItems_3599018e-8304-445f-ad24-a6f68a99d522" xlink:to="loc_us-gaap_LesseeLeaseDescriptionTable_e2a7b6e7-f6b7-4ab4-8109-76af39420c06" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_fc21de76-d261-487e-ace9-8b71b70b80e1" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_RangeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LesseeLeaseDescriptionTable_e2a7b6e7-f6b7-4ab4-8109-76af39420c06" xlink:to="loc_srt_RangeAxis_fc21de76-d261-487e-ace9-8b71b70b80e1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_fc21de76-d261-487e-ace9-8b71b70b80e1_default" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_fc21de76-d261-487e-ace9-8b71b70b80e1" xlink:to="loc_srt_RangeMember_fc21de76-d261-487e-ace9-8b71b70b80e1_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_6085fe8b-50ee-4b11-b113-5a2b4d497654" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_fc21de76-d261-487e-ace9-8b71b70b80e1" xlink:to="loc_srt_RangeMember_6085fe8b-50ee-4b11-b113-5a2b4d497654" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MinimumMember_b6fe273f-c7fe-40ea-9c06-0fc6e8d4baf0" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_MinimumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_6085fe8b-50ee-4b11-b113-5a2b4d497654" xlink:to="loc_srt_MinimumMember_b6fe273f-c7fe-40ea-9c06-0fc6e8d4baf0" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MaximumMember_4da6665d-96e9-4586-8e70-604470c08756" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_MaximumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_6085fe8b-50ee-4b11-b113-5a2b4d497654" xlink:to="loc_srt_MaximumMember_4da6665d-96e9-4586-8e70-604470c08756" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://brilliantearth.com/role/DebtTermLoanDetails" xlink:type="simple" xlink:href="brlt-20230331.xsd#DebtTermLoanDetails"/>
  <link:definitionLink xlink:role="http://brilliantearth.com/role/DebtTermLoanDetails" xlink:type="extended" id="if9710655c9584b7f9079de5729701952_DebtTermLoanDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentLineItems_9e853a14-8615-432d-a393-3fbe67b09880" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentCarryingAmount_c89f29c2-ab89-42ae-8256-77c35df2a9e6" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentCarryingAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_9e853a14-8615-432d-a393-3fbe67b09880" xlink:to="loc_us-gaap_DebtInstrumentCarryingAmount_c89f29c2-ab89-42ae-8256-77c35df2a9e6" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredFinanceCostsNet_cd830e35-e013-4c43-b45e-885d45988111" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DeferredFinanceCostsNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_9e853a14-8615-432d-a393-3fbe67b09880" xlink:to="loc_us-gaap_DeferredFinanceCostsNet_cd830e35-e013-4c43-b45e-885d45988111" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebt_95686efd-794e-45df-af54-5cbdb78eadc9" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LongTermDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_9e853a14-8615-432d-a393-3fbe67b09880" xlink:to="loc_us-gaap_LongTermDebt_95686efd-794e-45df-af54-5cbdb78eadc9" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebtCurrent_6c3ff400-f771-4724-a2be-8c9a5813e42a" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LongTermDebtCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_9e853a14-8615-432d-a393-3fbe67b09880" xlink:to="loc_us-gaap_LongTermDebtCurrent_6c3ff400-f771-4724-a2be-8c9a5813e42a" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_brlt_LongTermDebtExcludingCurrentMaturitiesGross_64f78259-7c93-4eb9-bac1-0cb5bb031371" xlink:href="brlt-20230331.xsd#brlt_LongTermDebtExcludingCurrentMaturitiesGross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_9e853a14-8615-432d-a393-3fbe67b09880" xlink:to="loc_brlt_LongTermDebtExcludingCurrentMaturitiesGross_64f78259-7c93-4eb9-bac1-0cb5bb031371" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebtNoncurrent_d9762269-1fb3-47bc-a7fe-4d05ed682f06" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LongTermDebtNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_9e853a14-8615-432d-a393-3fbe67b09880" xlink:to="loc_us-gaap_LongTermDebtNoncurrent_d9762269-1fb3-47bc-a7fe-4d05ed682f06" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentTable_32af7231-3373-496f-a1b0-b567151c0c84" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DebtInstrumentLineItems_9e853a14-8615-432d-a393-3fbe67b09880" xlink:to="loc_us-gaap_DebtInstrumentTable_32af7231-3373-496f-a1b0-b567151c0c84" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_416e1b19-97eb-4809-9289-e45f22fdaf0e" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LongtermDebtTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_32af7231-3373-496f-a1b0-b567151c0c84" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_416e1b19-97eb-4809-9289-e45f22fdaf0e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_416e1b19-97eb-4809-9289-e45f22fdaf0e_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_416e1b19-97eb-4809-9289-e45f22fdaf0e" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_416e1b19-97eb-4809-9289-e45f22fdaf0e_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_3b945d5e-5a7b-4ac0-aa17-1898f4d6939f" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_416e1b19-97eb-4809-9289-e45f22fdaf0e" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_3b945d5e-5a7b-4ac0-aa17-1898f4d6939f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SecuredDebtMember_516934df-941f-4566-b1f9-1b89605d2a95" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_SecuredDebtMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_3b945d5e-5a7b-4ac0-aa17-1898f4d6939f" xlink:to="loc_us-gaap_SecuredDebtMember_516934df-941f-4566-b1f9-1b89605d2a95" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentAxis_6520cc17-060e-4dc2-96b0-e1c89adb8571" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_32af7231-3373-496f-a1b0-b567151c0c84" xlink:to="loc_us-gaap_DebtInstrumentAxis_6520cc17-060e-4dc2-96b0-e1c89adb8571" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_6520cc17-060e-4dc2-96b0-e1c89adb8571_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_6520cc17-060e-4dc2-96b0-e1c89adb8571" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_6520cc17-060e-4dc2-96b0-e1c89adb8571_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_45f99ce0-18b3-4497-b647-0552a47578b2" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_6520cc17-060e-4dc2-96b0-e1c89adb8571" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_45f99ce0-18b3-4497-b647-0552a47578b2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_brlt_TermLoanAgreementMember_513bf6b7-6133-407b-969b-48e8b7dc2ed7" xlink:href="brlt-20230331.xsd#brlt_TermLoanAgreementMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_45f99ce0-18b3-4497-b647-0552a47578b2" xlink:to="loc_brlt_TermLoanAgreementMember_513bf6b7-6133-407b-969b-48e8b7dc2ed7" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://brilliantearth.com/role/DebtNarrativeDetails" xlink:type="simple" xlink:href="brlt-20230331.xsd#DebtNarrativeDetails"/>
  <link:definitionLink xlink:role="http://brilliantearth.com/role/DebtNarrativeDetails" xlink:type="extended" id="ied18bcc8af7348a2b6d7f6e48ff655ea_DebtNarrativeDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentLineItems_6fecaa19-6f44-485c-b306-0ea5b80fa52d" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_brlt_DebtInstrumentPrepaymentFeePercent_e037e18f-898a-4a90-9994-73cb35c704a9" xlink:href="brlt-20230331.xsd#brlt_DebtInstrumentPrepaymentFeePercent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_6fecaa19-6f44-485c-b306-0ea5b80fa52d" xlink:to="loc_brlt_DebtInstrumentPrepaymentFeePercent_e037e18f-898a-4a90-9994-73cb35c704a9" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_brlt_DebtInstrumentVariableRateFloor_c338d239-0417-4ec6-830f-19b5e089f525" xlink:href="brlt-20230331.xsd#brlt_DebtInstrumentVariableRateFloor"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_6fecaa19-6f44-485c-b306-0ea5b80fa52d" xlink:to="loc_brlt_DebtInstrumentVariableRateFloor_c338d239-0417-4ec6-830f-19b5e089f525" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentBasisSpreadOnVariableRate1_aa3fb622-cb2d-4b19-a1b4-9ec193e7db86" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentBasisSpreadOnVariableRate1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_6fecaa19-6f44-485c-b306-0ea5b80fa52d" xlink:to="loc_us-gaap_DebtInstrumentBasisSpreadOnVariableRate1_aa3fb622-cb2d-4b19-a1b4-9ec193e7db86" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfWarrantOrRightNumberOfSecuritiesCalledByWarrantsOrRights_fcd03203-9b2f-484c-b63a-1a6dd5253825" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ClassOfWarrantOrRightNumberOfSecuritiesCalledByWarrantsOrRights"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_6fecaa19-6f44-485c-b306-0ea5b80fa52d" xlink:to="loc_us-gaap_ClassOfWarrantOrRightNumberOfSecuritiesCalledByWarrantsOrRights_fcd03203-9b2f-484c-b63a-1a6dd5253825" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_brlt_WarrantLiabilityFairValueDisclosure_7c43fee4-ab0b-4153-8c62-f80e0651a9c9" xlink:href="brlt-20230331.xsd#brlt_WarrantLiabilityFairValueDisclosure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_6fecaa19-6f44-485c-b306-0ea5b80fa52d" xlink:to="loc_brlt_WarrantLiabilityFairValueDisclosure_7c43fee4-ab0b-4153-8c62-f80e0651a9c9" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_brlt_DebtInstrumentFinalPrepaymentFeePercentOfPrincipalAmount_e7cee80a-0f7a-4553-a7f4-15c4788a1e38" xlink:href="brlt-20230331.xsd#brlt_DebtInstrumentFinalPrepaymentFeePercentOfPrincipalAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_6fecaa19-6f44-485c-b306-0ea5b80fa52d" xlink:to="loc_brlt_DebtInstrumentFinalPrepaymentFeePercentOfPrincipalAmount_e7cee80a-0f7a-4553-a7f4-15c4788a1e38" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_brlt_DebtInstrumentFinalPrepaymentFee_9c41a2ca-d085-4140-8f70-106408bdabf9" xlink:href="brlt-20230331.xsd#brlt_DebtInstrumentFinalPrepaymentFee"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_6fecaa19-6f44-485c-b306-0ea5b80fa52d" xlink:to="loc_brlt_DebtInstrumentFinalPrepaymentFee_9c41a2ca-d085-4140-8f70-106408bdabf9" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EarlyRepaymentOfSeniorDebt_6a88161e-274a-4e9c-a5b9-e0213bed2554" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_EarlyRepaymentOfSeniorDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_6fecaa19-6f44-485c-b306-0ea5b80fa52d" xlink:to="loc_us-gaap_EarlyRepaymentOfSeniorDebt_6a88161e-274a-4e9c-a5b9-e0213bed2554" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GainsLossesOnExtinguishmentOfDebt_e92a08c3-4ba4-4981-a7dd-1811e6b26468" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_GainsLossesOnExtinguishmentOfDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_6fecaa19-6f44-485c-b306-0ea5b80fa52d" xlink:to="loc_us-gaap_GainsLossesOnExtinguishmentOfDebt_e92a08c3-4ba4-4981-a7dd-1811e6b26468" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentFaceAmount_462a2db7-1925-4436-90b0-efc85012f329" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentFaceAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_6fecaa19-6f44-485c-b306-0ea5b80fa52d" xlink:to="loc_us-gaap_DebtInstrumentFaceAmount_462a2db7-1925-4436-90b0-efc85012f329" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity_7b6a3dcd-d9f9-42ff-b114-a84a11355e99" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_6fecaa19-6f44-485c-b306-0ea5b80fa52d" xlink:to="loc_us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity_7b6a3dcd-d9f9-42ff-b114-a84a11355e99" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_brlt_DebtInstrumentAnnualAdjustmentPercent_10d6235e-c481-4611-803b-0fa4eec4ba77" xlink:href="brlt-20230331.xsd#brlt_DebtInstrumentAnnualAdjustmentPercent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_6fecaa19-6f44-485c-b306-0ea5b80fa52d" xlink:to="loc_brlt_DebtInstrumentAnnualAdjustmentPercent_10d6235e-c481-4611-803b-0fa4eec4ba77" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityUnusedCapacityCommitmentFeePercentage_6bb28822-081f-49df-8014-a6f69b8d634e" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LineOfCreditFacilityUnusedCapacityCommitmentFeePercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_6fecaa19-6f44-485c-b306-0ea5b80fa52d" xlink:to="loc_us-gaap_LineOfCreditFacilityUnusedCapacityCommitmentFeePercentage_6bb28822-081f-49df-8014-a6f69b8d634e" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_brlt_LineOfCreditFacilityPeriodicPaymentQuarterlyPaymentPercentPeriodOne_2af25abb-ffc9-48fd-9377-41253981117b" xlink:href="brlt-20230331.xsd#brlt_LineOfCreditFacilityPeriodicPaymentQuarterlyPaymentPercentPeriodOne"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_6fecaa19-6f44-485c-b306-0ea5b80fa52d" xlink:to="loc_brlt_LineOfCreditFacilityPeriodicPaymentQuarterlyPaymentPercentPeriodOne_2af25abb-ffc9-48fd-9377-41253981117b" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_brlt_LineOfCreditFacilityPeriodicPaymentQuarterlyPaymentPercentPeriodTwo_9923174d-1224-4740-9d43-656a0ebd95e7" xlink:href="brlt-20230331.xsd#brlt_LineOfCreditFacilityPeriodicPaymentQuarterlyPaymentPercentPeriodTwo"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_6fecaa19-6f44-485c-b306-0ea5b80fa52d" xlink:to="loc_brlt_LineOfCreditFacilityPeriodicPaymentQuarterlyPaymentPercentPeriodTwo_9923174d-1224-4740-9d43-656a0ebd95e7" xlink:type="arc" order="14"/>
    <link:loc xlink:type="locator" xlink:label="loc_brlt_LineOfCreditFacilityPeriodicPaymentQuarterlyPaymentPercentPeriodThree_ae66ed32-4bb8-404c-a52b-3a751e1eef66" xlink:href="brlt-20230331.xsd#brlt_LineOfCreditFacilityPeriodicPaymentQuarterlyPaymentPercentPeriodThree"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_6fecaa19-6f44-485c-b306-0ea5b80fa52d" xlink:to="loc_brlt_LineOfCreditFacilityPeriodicPaymentQuarterlyPaymentPercentPeriodThree_ae66ed32-4bb8-404c-a52b-3a751e1eef66" xlink:type="arc" order="15"/>
    <link:loc xlink:type="locator" xlink:label="loc_brlt_DebtInstrumentCovenantComplianceFixedChargeCoverageRatioPercent_1ff8fb16-5741-467c-bc8f-2cf2779a9b83" xlink:href="brlt-20230331.xsd#brlt_DebtInstrumentCovenantComplianceFixedChargeCoverageRatioPercent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_6fecaa19-6f44-485c-b306-0ea5b80fa52d" xlink:to="loc_brlt_DebtInstrumentCovenantComplianceFixedChargeCoverageRatioPercent_1ff8fb16-5741-467c-bc8f-2cf2779a9b83" xlink:type="arc" order="16"/>
    <link:loc xlink:type="locator" xlink:label="loc_brlt_DebtInstrumentCovenantComplianceConsolidatedTotalLeverageRatioPercent_c37eb1ba-67fa-49dd-92dc-58561707eda7" xlink:href="brlt-20230331.xsd#brlt_DebtInstrumentCovenantComplianceConsolidatedTotalLeverageRatioPercent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_6fecaa19-6f44-485c-b306-0ea5b80fa52d" xlink:to="loc_brlt_DebtInstrumentCovenantComplianceConsolidatedTotalLeverageRatioPercent_c37eb1ba-67fa-49dd-92dc-58561707eda7" xlink:type="arc" order="17"/>
    <link:loc xlink:type="locator" xlink:label="loc_brlt_DebtInstrumentCovenantComplianceConsolidatedBorrowerLeverageRatioPercent_8794e40f-4d54-4f59-b6ed-9f22eb3d3791" xlink:href="brlt-20230331.xsd#brlt_DebtInstrumentCovenantComplianceConsolidatedBorrowerLeverageRatioPercent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_6fecaa19-6f44-485c-b306-0ea5b80fa52d" xlink:to="loc_brlt_DebtInstrumentCovenantComplianceConsolidatedBorrowerLeverageRatioPercent_8794e40f-4d54-4f59-b6ed-9f22eb3d3791" xlink:type="arc" order="18"/>
    <link:loc xlink:type="locator" xlink:label="loc_brlt_DebtInstrumentCovenantComplianceConsolidatedBorrowerLeverageRatioTemporaryIncreasedAmountPercent_a9ee4764-a30f-458b-8fbb-3ec9b5e8a3bb" xlink:href="brlt-20230331.xsd#brlt_DebtInstrumentCovenantComplianceConsolidatedBorrowerLeverageRatioTemporaryIncreasedAmountPercent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_6fecaa19-6f44-485c-b306-0ea5b80fa52d" xlink:to="loc_brlt_DebtInstrumentCovenantComplianceConsolidatedBorrowerLeverageRatioTemporaryIncreasedAmountPercent_a9ee4764-a30f-458b-8fbb-3ec9b5e8a3bb" xlink:type="arc" order="19"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredFinanceCostsNoncurrentNet_468fa198-0ef2-4d45-b37f-28f615d56a4b" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DeferredFinanceCostsNoncurrentNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_6fecaa19-6f44-485c-b306-0ea5b80fa52d" xlink:to="loc_us-gaap_DeferredFinanceCostsNoncurrentNet_468fa198-0ef2-4d45-b37f-28f615d56a4b" xlink:type="arc" order="20"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedAmortizationDeferredFinanceCosts_8b1b9cfb-6f2a-4643-a917-1ce8ef029cff" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AccumulatedAmortizationDeferredFinanceCosts"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_6fecaa19-6f44-485c-b306-0ea5b80fa52d" xlink:to="loc_us-gaap_AccumulatedAmortizationDeferredFinanceCosts_8b1b9cfb-6f2a-4643-a917-1ce8ef029cff" xlink:type="arc" order="21"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedAmortizationOfNoncurrentDeferredFinanceCosts_07d52b5e-7d82-4e7f-8ac6-a33ebaa4675c" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AccumulatedAmortizationOfNoncurrentDeferredFinanceCosts"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_6fecaa19-6f44-485c-b306-0ea5b80fa52d" xlink:to="loc_us-gaap_AccumulatedAmortizationOfNoncurrentDeferredFinanceCosts_07d52b5e-7d82-4e7f-8ac6-a33ebaa4675c" xlink:type="arc" order="22"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentInterestRateDuringPeriod_7103427d-0015-4dcb-bf5a-82fea7a882a6" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentInterestRateDuringPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_6fecaa19-6f44-485c-b306-0ea5b80fa52d" xlink:to="loc_us-gaap_DebtInstrumentInterestRateDuringPeriod_7103427d-0015-4dcb-bf5a-82fea7a882a6" xlink:type="arc" order="23"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestExpenseDebt_95f8af0a-aebf-4627-9779-2ff1687d34eb" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_InterestExpenseDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_6fecaa19-6f44-485c-b306-0ea5b80fa52d" xlink:to="loc_us-gaap_InterestExpenseDebt_95f8af0a-aebf-4627-9779-2ff1687d34eb" xlink:type="arc" order="24"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AmortizationOfFinancingCosts_24f6aeff-ce6b-4869-808e-4255c32a90c8" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AmortizationOfFinancingCosts"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_6fecaa19-6f44-485c-b306-0ea5b80fa52d" xlink:to="loc_us-gaap_AmortizationOfFinancingCosts_24f6aeff-ce6b-4869-808e-4255c32a90c8" xlink:type="arc" order="25"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCredit_6e44ce0b-0ca7-4ddc-91aa-a5fd310f24d3" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LineOfCredit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_6fecaa19-6f44-485c-b306-0ea5b80fa52d" xlink:to="loc_us-gaap_LineOfCredit_6e44ce0b-0ca7-4ddc-91aa-a5fd310f24d3" xlink:type="arc" order="26"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentTable_636ec9b4-1ce0-461b-bac7-ac3ac2188f0f" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DebtInstrumentLineItems_6fecaa19-6f44-485c-b306-0ea5b80fa52d" xlink:to="loc_us-gaap_DebtInstrumentTable_636ec9b4-1ce0-461b-bac7-ac3ac2188f0f" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentAxis_7f26c9d2-6960-4789-b4cb-46f7c6d8a90d" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_636ec9b4-1ce0-461b-bac7-ac3ac2188f0f" xlink:to="loc_us-gaap_DebtInstrumentAxis_7f26c9d2-6960-4789-b4cb-46f7c6d8a90d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_7f26c9d2-6960-4789-b4cb-46f7c6d8a90d_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_7f26c9d2-6960-4789-b4cb-46f7c6d8a90d" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_7f26c9d2-6960-4789-b4cb-46f7c6d8a90d_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_3f913bd1-980d-4a05-939d-46b7758538b2" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_7f26c9d2-6960-4789-b4cb-46f7c6d8a90d" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_3f913bd1-980d-4a05-939d-46b7758538b2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_brlt_RunwayTermLoanAgreementMember_6d502a20-f178-436b-a149-c7bdc90ff0ca" xlink:href="brlt-20230331.xsd#brlt_RunwayTermLoanAgreementMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_3f913bd1-980d-4a05-939d-46b7758538b2" xlink:to="loc_brlt_RunwayTermLoanAgreementMember_6d502a20-f178-436b-a149-c7bdc90ff0ca" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_brlt_TermLoanAgreementMember_ad7b3e7e-6993-4579-bbfa-c05e75b29552" xlink:href="brlt-20230331.xsd#brlt_TermLoanAgreementMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_3f913bd1-980d-4a05-939d-46b7758538b2" xlink:to="loc_brlt_TermLoanAgreementMember_ad7b3e7e-6993-4579-bbfa-c05e75b29552" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_551d2589-11f2-43e7-a9db-71bc7c58fd58" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LongtermDebtTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_636ec9b4-1ce0-461b-bac7-ac3ac2188f0f" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_551d2589-11f2-43e7-a9db-71bc7c58fd58" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_551d2589-11f2-43e7-a9db-71bc7c58fd58_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_551d2589-11f2-43e7-a9db-71bc7c58fd58" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_551d2589-11f2-43e7-a9db-71bc7c58fd58_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_30ee3ae9-7424-42b7-9640-b2c0dbb0f4e4" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_551d2589-11f2-43e7-a9db-71bc7c58fd58" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_30ee3ae9-7424-42b7-9640-b2c0dbb0f4e4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SecuredDebtMember_d1cce6fe-8141-4b51-8d0c-8cfb2d619950" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_SecuredDebtMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_30ee3ae9-7424-42b7-9640-b2c0dbb0f4e4" xlink:to="loc_us-gaap_SecuredDebtMember_d1cce6fe-8141-4b51-8d0c-8cfb2d619950" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditMember_4b71bc78-175f-4200-a0f8-ee8e6118ab0c" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LineOfCreditMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_30ee3ae9-7424-42b7-9640-b2c0dbb0f4e4" xlink:to="loc_us-gaap_LineOfCreditMember_4b71bc78-175f-4200-a0f8-ee8e6118ab0c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VariableRateAxis_7d6d6d6d-f523-4534-837b-c08e250a7c16" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_VariableRateAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_636ec9b4-1ce0-461b-bac7-ac3ac2188f0f" xlink:to="loc_us-gaap_VariableRateAxis_7d6d6d6d-f523-4534-837b-c08e250a7c16" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VariableRateDomain_7d6d6d6d-f523-4534-837b-c08e250a7c16_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_VariableRateDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_VariableRateAxis_7d6d6d6d-f523-4534-837b-c08e250a7c16" xlink:to="loc_us-gaap_VariableRateDomain_7d6d6d6d-f523-4534-837b-c08e250a7c16_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VariableRateDomain_915b5d80-fff7-4aa1-afc1-9555041b9d4b" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_VariableRateDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_VariableRateAxis_7d6d6d6d-f523-4534-837b-c08e250a7c16" xlink:to="loc_us-gaap_VariableRateDomain_915b5d80-fff7-4aa1-afc1-9555041b9d4b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LondonInterbankOfferedRateLIBORMember_7ea9085f-575a-4908-83d4-91f94e199e30" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LondonInterbankOfferedRateLIBORMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VariableRateDomain_915b5d80-fff7-4aa1-afc1-9555041b9d4b" xlink:to="loc_us-gaap_LondonInterbankOfferedRateLIBORMember_7ea9085f-575a-4908-83d4-91f94e199e30" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SecuredOvernightFinancingRateSofrOvernightIndexSwapRateMember_05957d0c-4a7f-42e6-85a0-306d88e1f1ac" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_SecuredOvernightFinancingRateSofrOvernightIndexSwapRateMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VariableRateDomain_915b5d80-fff7-4aa1-afc1-9555041b9d4b" xlink:to="loc_us-gaap_SecuredOvernightFinancingRateSofrOvernightIndexSwapRateMember_05957d0c-4a7f-42e6-85a0-306d88e1f1ac" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_brlt_AlternativeBaseRateMember_c012985e-5e1e-4704-b2da-b89f9e4a11e4" xlink:href="brlt-20230331.xsd#brlt_AlternativeBaseRateMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VariableRateDomain_915b5d80-fff7-4aa1-afc1-9555041b9d4b" xlink:to="loc_brlt_AlternativeBaseRateMember_c012985e-5e1e-4704-b2da-b89f9e4a11e4" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_4b3fa6e7-e3a9-443c-bc93-d9e260b696b1" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_RangeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_636ec9b4-1ce0-461b-bac7-ac3ac2188f0f" xlink:to="loc_srt_RangeAxis_4b3fa6e7-e3a9-443c-bc93-d9e260b696b1" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_4b3fa6e7-e3a9-443c-bc93-d9e260b696b1_default" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_4b3fa6e7-e3a9-443c-bc93-d9e260b696b1" xlink:to="loc_srt_RangeMember_4b3fa6e7-e3a9-443c-bc93-d9e260b696b1_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_23b2de26-0dd3-404e-afaa-2f6d3b9060d4" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_4b3fa6e7-e3a9-443c-bc93-d9e260b696b1" xlink:to="loc_srt_RangeMember_23b2de26-0dd3-404e-afaa-2f6d3b9060d4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MaximumMember_82bbbdaa-92cd-4b3a-affe-a58c12d44e8b" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_MaximumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_23b2de26-0dd3-404e-afaa-2f6d3b9060d4" xlink:to="loc_srt_MaximumMember_82bbbdaa-92cd-4b3a-affe-a58c12d44e8b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MinimumMember_c1f864ae-bab7-4183-9b44-5802ecfbf8b9" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_MinimumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_23b2de26-0dd3-404e-afaa-2f6d3b9060d4" xlink:to="loc_srt_MinimumMember_c1f864ae-bab7-4183-9b44-5802ecfbf8b9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfWarrantOrRightAxis_19859e38-0577-489e-bc33-b17e28ff1959" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ClassOfWarrantOrRightAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_636ec9b4-1ce0-461b-bac7-ac3ac2188f0f" xlink:to="loc_us-gaap_ClassOfWarrantOrRightAxis_19859e38-0577-489e-bc33-b17e28ff1959" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfWarrantOrRightDomain_19859e38-0577-489e-bc33-b17e28ff1959_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ClassOfWarrantOrRightDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ClassOfWarrantOrRightAxis_19859e38-0577-489e-bc33-b17e28ff1959" xlink:to="loc_us-gaap_ClassOfWarrantOrRightDomain_19859e38-0577-489e-bc33-b17e28ff1959_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfWarrantOrRightDomain_72b4aca9-2b95-43a8-b3f5-1e94b35d6609" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ClassOfWarrantOrRightDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ClassOfWarrantOrRightAxis_19859e38-0577-489e-bc33-b17e28ff1959" xlink:to="loc_us-gaap_ClassOfWarrantOrRightDomain_72b4aca9-2b95-43a8-b3f5-1e94b35d6609" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_brlt_ClassPWarrantsMember_f33ea34a-81b8-4166-889e-9e6ecf14d42b" xlink:href="brlt-20230331.xsd#brlt_ClassPWarrantsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfWarrantOrRightDomain_72b4aca9-2b95-43a8-b3f5-1e94b35d6609" xlink:to="loc_brlt_ClassPWarrantsMember_f33ea34a-81b8-4166-889e-9e6ecf14d42b" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://brilliantearth.com/role/EquityBasedCompensationNarrativeDetails" xlink:type="simple" xlink:href="brlt-20230331.xsd#EquityBasedCompensationNarrativeDetails"/>
  <link:definitionLink xlink:role="http://brilliantearth.com/role/EquityBasedCompensationNarrativeDetails" xlink:type="extended" id="i4e8b00c4d45b4e05a43580745d5ed24b_EquityBasedCompensationNarrativeDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_cbdb2973-be12-483f-a4be-a5728c4d4bbc" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AllocatedShareBasedCompensationExpense_d4088dab-3a91-4914-b2c8-a673ee2c4b1f" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AllocatedShareBasedCompensationExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_cbdb2973-be12-483f-a4be-a5728c4d4bbc" xlink:to="loc_us-gaap_AllocatedShareBasedCompensationExpense_d4088dab-3a91-4914-b2c8-a673ee2c4b1f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedShareBasedAwardsOtherThanOptions_e907c0b7-c498-4eef-858b-7464e2f0627e" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedShareBasedAwardsOtherThanOptions"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_cbdb2973-be12-483f-a4be-a5728c4d4bbc" xlink:to="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedShareBasedAwardsOtherThanOptions_e907c0b7-c498-4eef-858b-7464e2f0627e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1_9bb466e5-b54b-4f2c-bcc0-827aa984e7a0" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_cbdb2973-be12-483f-a4be-a5728c4d4bbc" xlink:to="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1_9bb466e5-b54b-4f2c-bcc0-827aa984e7a0" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedStockOptions_8be51119-c97b-4016-bddd-77ca6b4619d1" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedStockOptions"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_cbdb2973-be12-483f-a4be-a5728c4d4bbc" xlink:to="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedStockOptions_8be51119-c97b-4016-bddd-77ca6b4619d1" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_103ea716-9d53-4f3e-9753-c2f91a7f071b" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_cbdb2973-be12-483f-a4be-a5728c4d4bbc" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_103ea716-9d53-4f3e-9753-c2f91a7f071b" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AwardTypeAxis_26d65909-7283-4e5a-9232-eab3336f4672" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AwardTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_103ea716-9d53-4f3e-9753-c2f91a7f071b" xlink:to="loc_us-gaap_AwardTypeAxis_26d65909-7283-4e5a-9232-eab3336f4672" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_26d65909-7283-4e5a-9232-eab3336f4672_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_26d65909-7283-4e5a-9232-eab3336f4672" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_26d65909-7283-4e5a-9232-eab3336f4672_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_37e9c41e-d4e6-4501-a13a-a065fd813c4c" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_26d65909-7283-4e5a-9232-eab3336f4672" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_37e9c41e-d4e6-4501-a13a-a065fd813c4c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_brlt_LLCUnitsMember_41201f95-e099-438f-b558-edc2c61b5e66" xlink:href="brlt-20230331.xsd#brlt_LLCUnitsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_37e9c41e-d4e6-4501-a13a-a065fd813c4c" xlink:to="loc_brlt_LLCUnitsMember_41201f95-e099-438f-b558-edc2c61b5e66" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedStockUnitsRSUMember_472c9fbb-f91f-4de0-9dac-c71045aeba52" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_RestrictedStockUnitsRSUMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_37e9c41e-d4e6-4501-a13a-a065fd813c4c" xlink:to="loc_us-gaap_RestrictedStockUnitsRSUMember_472c9fbb-f91f-4de0-9dac-c71045aeba52" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeStockOptionMember_da5acf80-1905-413e-a40b-3af9bf878838" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_EmployeeStockOptionMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_37e9c41e-d4e6-4501-a13a-a065fd813c4c" xlink:to="loc_us-gaap_EmployeeStockOptionMember_da5acf80-1905-413e-a40b-3af9bf878838" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementLocationAxis_ef6d17b9-5d1a-4aa0-94e0-c8852a9578ce" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_IncomeStatementLocationAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_103ea716-9d53-4f3e-9753-c2f91a7f071b" xlink:to="loc_us-gaap_IncomeStatementLocationAxis_ef6d17b9-5d1a-4aa0-94e0-c8852a9578ce" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementLocationDomain_ef6d17b9-5d1a-4aa0-94e0-c8852a9578ce_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_IncomeStatementLocationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_IncomeStatementLocationAxis_ef6d17b9-5d1a-4aa0-94e0-c8852a9578ce" xlink:to="loc_us-gaap_IncomeStatementLocationDomain_ef6d17b9-5d1a-4aa0-94e0-c8852a9578ce_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementLocationDomain_d39293ce-9929-433d-bf4d-375aaac62415" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_IncomeStatementLocationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_IncomeStatementLocationAxis_ef6d17b9-5d1a-4aa0-94e0-c8852a9578ce" xlink:to="loc_us-gaap_IncomeStatementLocationDomain_d39293ce-9929-433d-bf4d-375aaac62415" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SellingGeneralAndAdministrativeExpensesMember_e7e77b08-1dcf-48da-9c37-8ad2412dcd6d" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_SellingGeneralAndAdministrativeExpensesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementLocationDomain_d39293ce-9929-433d-bf4d-375aaac62415" xlink:to="loc_us-gaap_SellingGeneralAndAdministrativeExpensesMember_e7e77b08-1dcf-48da-9c37-8ad2412dcd6d" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://brilliantearth.com/role/EquityBasedCompensationRSUActivityDetails" xlink:type="simple" xlink:href="brlt-20230331.xsd#EquityBasedCompensationRSUActivityDetails"/>
  <link:definitionLink xlink:role="http://brilliantearth.com/role/EquityBasedCompensationRSUActivityDetails" xlink:type="extended" id="ifcb8c645c18c4ba0ab4540aa2d7fa564_EquityBasedCompensationRSUActivityDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_6e42207f-a606-4720-b67c-57d940a27dea" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_fe5a6ff1-c4c1-47ed-bc22-b00b812b6446" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_6e42207f-a606-4720-b67c-57d940a27dea" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_fe5a6ff1-c4c1-47ed-bc22-b00b812b6446" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber_88bfc438-b945-4587-8669-d6e78ad1fbf9" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_fe5a6ff1-c4c1-47ed-bc22-b00b812b6446" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber_88bfc438-b945-4587-8669-d6e78ad1fbf9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod_eeecf064-485d-457b-983c-f09cf02cb4e9" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_fe5a6ff1-c4c1-47ed-bc22-b00b812b6446" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod_eeecf064-485d-457b-983c-f09cf02cb4e9" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod_59234816-6c40-4565-a47b-9ecfd83ae4f9" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_fe5a6ff1-c4c1-47ed-bc22-b00b812b6446" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod_59234816-6c40-4565-a47b-9ecfd83ae4f9" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod_3dfac3f4-80ea-48bd-aa7a-b35c0339845b" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_fe5a6ff1-c4c1-47ed-bc22-b00b812b6446" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod_3dfac3f4-80ea-48bd-aa7a-b35c0339845b" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber_162772ca-6ddc-4b0d-a63f-45ca714f37e7" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_c71b1e46-d1ee-4a2d-8158-7a45946d977a" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_6e42207f-a606-4720-b67c-57d940a27dea" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_c71b1e46-d1ee-4a2d-8158-7a45946d977a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue_a9f1649f-caa2-4046-8070-fd57acc679ac" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_c71b1e46-d1ee-4a2d-8158-7a45946d977a" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue_a9f1649f-caa2-4046-8070-fd57acc679ac" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_cc36d8a7-ee65-4909-9e07-18fb8f0c33f3" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_c71b1e46-d1ee-4a2d-8158-7a45946d977a" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_cc36d8a7-ee65-4909-9e07-18fb8f0c33f3" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue_0ba896a8-653c-44bc-a435-171228134ab4" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_c71b1e46-d1ee-4a2d-8158-7a45946d977a" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue_0ba896a8-653c-44bc-a435-171228134ab4" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue_03457f43-49ad-4003-ad93-13779da66696" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_c71b1e46-d1ee-4a2d-8158-7a45946d977a" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue_03457f43-49ad-4003-ad93-13779da66696" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue_40dedfe4-b81c-44a7-a25e-7f4c77f809ab" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_aaabdf20-035b-4bf0-b9f9-dc45ac6d2077" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_6e42207f-a606-4720-b67c-57d940a27dea" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_aaabdf20-035b-4bf0-b9f9-dc45ac6d2077" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AwardTypeAxis_0757468e-afe5-4523-b260-414cb1231f73" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AwardTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_aaabdf20-035b-4bf0-b9f9-dc45ac6d2077" xlink:to="loc_us-gaap_AwardTypeAxis_0757468e-afe5-4523-b260-414cb1231f73" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_0757468e-afe5-4523-b260-414cb1231f73_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_0757468e-afe5-4523-b260-414cb1231f73" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_0757468e-afe5-4523-b260-414cb1231f73_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_8f3af168-d634-44e8-9871-45340ff964c4" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_0757468e-afe5-4523-b260-414cb1231f73" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_8f3af168-d634-44e8-9871-45340ff964c4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedStockUnitsRSUMember_5f447fe9-79ed-4899-8511-1da83ebe4f24" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_RestrictedStockUnitsRSUMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_8f3af168-d634-44e8-9871-45340ff964c4" xlink:to="loc_us-gaap_RestrictedStockUnitsRSUMember_5f447fe9-79ed-4899-8511-1da83ebe4f24" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://brilliantearth.com/role/EquityBasedCompensationLLCUnitActivityDetails" xlink:type="simple" xlink:href="brlt-20230331.xsd#EquityBasedCompensationLLCUnitActivityDetails"/>
  <link:definitionLink xlink:role="http://brilliantearth.com/role/EquityBasedCompensationLLCUnitActivityDetails" xlink:type="extended" id="i2f0bb89443504280bd0e82a82be56f92_EquityBasedCompensationLLCUnitActivityDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_0a4e9512-bb7b-4dd4-a5e8-5bd7228b6f58" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_65034df7-7f4e-4597-a05c-1a2a9eb0ccd6" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_0a4e9512-bb7b-4dd4-a5e8-5bd7228b6f58" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_65034df7-7f4e-4597-a05c-1a2a9eb0ccd6" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber_7a16083d-4204-4b00-b6ef-854a0a1e794e" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_65034df7-7f4e-4597-a05c-1a2a9eb0ccd6" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber_7a16083d-4204-4b00-b6ef-854a0a1e794e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod_463dbf64-f1b0-4105-8596-016390e00422" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_65034df7-7f4e-4597-a05c-1a2a9eb0ccd6" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod_463dbf64-f1b0-4105-8596-016390e00422" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod_3656683a-06a2-44ac-99d6-a4ae1f059cb6" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_65034df7-7f4e-4597-a05c-1a2a9eb0ccd6" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod_3656683a-06a2-44ac-99d6-a4ae1f059cb6" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber_47dd89b0-5247-4b04-9762-9b135499b523" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_be6ba82d-e52b-444b-91a0-8a2cb74ea682" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_0a4e9512-bb7b-4dd4-a5e8-5bd7228b6f58" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_be6ba82d-e52b-444b-91a0-8a2cb74ea682" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue_f0546b1b-a5d8-4683-9ade-f7ae91db9059" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_be6ba82d-e52b-444b-91a0-8a2cb74ea682" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue_f0546b1b-a5d8-4683-9ade-f7ae91db9059" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue_00139dd2-5d6e-4a94-beee-bc6e2c7ed95a" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_be6ba82d-e52b-444b-91a0-8a2cb74ea682" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue_00139dd2-5d6e-4a94-beee-bc6e2c7ed95a" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue_e3a71531-b51f-4756-b555-0e152b36bd5d" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_be6ba82d-e52b-444b-91a0-8a2cb74ea682" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue_e3a71531-b51f-4756-b555-0e152b36bd5d" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue_e42596f4-081b-4252-8a97-80080bd9cc97" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_e97b8d4b-c77c-4426-bdd9-c8570f2582a8" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_0a4e9512-bb7b-4dd4-a5e8-5bd7228b6f58" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_e97b8d4b-c77c-4426-bdd9-c8570f2582a8" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AwardTypeAxis_db97fa8c-0cfd-434b-a45b-b32214b28296" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AwardTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_e97b8d4b-c77c-4426-bdd9-c8570f2582a8" xlink:to="loc_us-gaap_AwardTypeAxis_db97fa8c-0cfd-434b-a45b-b32214b28296" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_db97fa8c-0cfd-434b-a45b-b32214b28296_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_db97fa8c-0cfd-434b-a45b-b32214b28296" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_db97fa8c-0cfd-434b-a45b-b32214b28296_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_372f6dec-5252-4b39-ba87-d44b248fc0f0" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_db97fa8c-0cfd-434b-a45b-b32214b28296" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_372f6dec-5252-4b39-ba87-d44b248fc0f0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_brlt_LLCUnitsMember_76470459-1984-4433-bc91-0c224b5e455a" xlink:href="brlt-20230331.xsd#brlt_LLCUnitsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_372f6dec-5252-4b39-ba87-d44b248fc0f0" xlink:to="loc_brlt_LLCUnitsMember_76470459-1984-4433-bc91-0c224b5e455a" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://brilliantearth.com/role/IncomeTaxesandTaxReceivableAgreementNarrativeDetails" xlink:type="simple" xlink:href="brlt-20230331.xsd#IncomeTaxesandTaxReceivableAgreementNarrativeDetails"/>
  <link:definitionLink xlink:role="http://brilliantearth.com/role/IncomeTaxesandTaxReceivableAgreementNarrativeDetails" xlink:type="extended" id="i580db147715b48688449c031b4ec5b07_IncomeTaxesandTaxReceivableAgreementNarrativeDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxExaminationLineItems_f9217ee1-7c60-4da0-8ed7-72b19cf610b6" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_IncomeTaxExaminationLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EffectiveIncomeTaxRateContinuingOperations_7834d2d0-c749-41ed-90cb-250393cde8ba" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_EffectiveIncomeTaxRateContinuingOperations"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeTaxExaminationLineItems_f9217ee1-7c60-4da0-8ed7-72b19cf610b6" xlink:to="loc_us-gaap_EffectiveIncomeTaxRateContinuingOperations_7834d2d0-c749-41ed-90cb-250393cde8ba" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_brlt_DeferredTaxAssetParentsBasis_e8a9c5e0-e210-44c2-80f0-e63374308685" xlink:href="brlt-20230331.xsd#brlt_DeferredTaxAssetParentsBasis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeTaxExaminationLineItems_f9217ee1-7c60-4da0-8ed7-72b19cf610b6" xlink:to="loc_brlt_DeferredTaxAssetParentsBasis_e8a9c5e0-e210-44c2-80f0-e63374308685" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxExpenseBenefit_a63d140b-11fe-4362-b6d5-4b3e183090db" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_IncomeTaxExpenseBenefit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeTaxExaminationLineItems_f9217ee1-7c60-4da0-8ed7-72b19cf610b6" xlink:to="loc_us-gaap_IncomeTaxExpenseBenefit_a63d140b-11fe-4362-b6d5-4b3e183090db" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_brlt_NoncontrollingInterestTaxBenefitDistributionsToNoncontrollingInterestHoldersPercent_b8b74e65-f201-4f3f-bbce-01a64ef46594" xlink:href="brlt-20230331.xsd#brlt_NoncontrollingInterestTaxBenefitDistributionsToNoncontrollingInterestHoldersPercent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeTaxExaminationLineItems_f9217ee1-7c60-4da0-8ed7-72b19cf610b6" xlink:to="loc_brlt_NoncontrollingInterestTaxBenefitDistributionsToNoncontrollingInterestHoldersPercent_b8b74e65-f201-4f3f-bbce-01a64ef46594" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_brlt_DeferredIncomeTaxAssetsRelatedToTaxReceivableAgreement_229e1b6c-036b-4aac-b9e5-35b84fec20af" xlink:href="brlt-20230331.xsd#brlt_DeferredIncomeTaxAssetsRelatedToTaxReceivableAgreement"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeTaxExaminationLineItems_f9217ee1-7c60-4da0-8ed7-72b19cf610b6" xlink:to="loc_brlt_DeferredIncomeTaxAssetsRelatedToTaxReceivableAgreement_229e1b6c-036b-4aac-b9e5-35b84fec20af" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_brlt_TaxReceivableAgreementLiabilityNoncurrent_7a41add9-4046-46b4-9092-96ab78b6fd8b" xlink:href="brlt-20230331.xsd#brlt_TaxReceivableAgreementLiabilityNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeTaxExaminationLineItems_f9217ee1-7c60-4da0-8ed7-72b19cf610b6" xlink:to="loc_brlt_TaxReceivableAgreementLiabilityNoncurrent_7a41add9-4046-46b4-9092-96ab78b6fd8b" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_brlt_TaxReceivableAgreementRecognitionInAdditionalPaidInCapitalRedemptionOfInterest_de1d5d43-acfd-4628-aad9-5fe22dfeff27" xlink:href="brlt-20230331.xsd#brlt_TaxReceivableAgreementRecognitionInAdditionalPaidInCapitalRedemptionOfInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeTaxExaminationLineItems_f9217ee1-7c60-4da0-8ed7-72b19cf610b6" xlink:to="loc_brlt_TaxReceivableAgreementRecognitionInAdditionalPaidInCapitalRedemptionOfInterest_de1d5d43-acfd-4628-aad9-5fe22dfeff27" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxExaminationTable_5ef7f75f-7d68-412a-a920-cff392755346" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_IncomeTaxExaminationTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_IncomeTaxExaminationLineItems_f9217ee1-7c60-4da0-8ed7-72b19cf610b6" xlink:to="loc_us-gaap_IncomeTaxExaminationTable_5ef7f75f-7d68-412a-a920-cff392755346" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_edf9aba8-4c56-400d-8ccc-8e7472b119c0" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_RangeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_IncomeTaxExaminationTable_5ef7f75f-7d68-412a-a920-cff392755346" xlink:to="loc_srt_RangeAxis_edf9aba8-4c56-400d-8ccc-8e7472b119c0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_edf9aba8-4c56-400d-8ccc-8e7472b119c0_default" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_edf9aba8-4c56-400d-8ccc-8e7472b119c0" xlink:to="loc_srt_RangeMember_edf9aba8-4c56-400d-8ccc-8e7472b119c0_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_30c7a3d7-f89a-4bcf-801e-a08a06f787f5" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_edf9aba8-4c56-400d-8ccc-8e7472b119c0" xlink:to="loc_srt_RangeMember_30c7a3d7-f89a-4bcf-801e-a08a06f787f5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MaximumMember_95ac5de1-6554-4c4c-8c02-21e2965c1674" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_MaximumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_30c7a3d7-f89a-4bcf-801e-a08a06f787f5" xlink:to="loc_srt_MaximumMember_95ac5de1-6554-4c4c-8c02-21e2965c1674" xlink:type="arc" order="0"/>
  </link:definitionLink>
</link:linkbase>
