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

<!--XBRL Document Created with the Workiva Platform-->
<!--Copyright 2026 Workiva-->
<!--r:019e2b1c-f606-74de-8ba8-971f867203fc,g:b87f22d9-67d0-4d2a-9d21-a3203052098c-->
<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://www.cycurion.com/role/Cover" xlink:type="simple" xlink:href="cycu-20260814.xsd#Cover"/>
  <link:definitionLink xlink:role="http://www.cycurion.com/role/Cover" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentInformationLineItems_019e2b1c-f606-731e-bf9b-da867c14245f" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_DocumentInformationLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentInformationTable_019e2b1c-f606-75c1-9d7c-6041585dd421" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_DocumentInformationTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_dei_DocumentInformationLineItems_019e2b1c-f606-731e-bf9b-da867c14245f" xlink:to="loc_dei_DocumentInformationTable_019e2b1c-f606-75c1-9d7c-6041585dd421" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementEquityComponentsAxis_019e2b1c-f606-73c9-a3fe-1ff363cd7774" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StatementEquityComponentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_dei_DocumentInformationTable_019e2b1c-f606-75c1-9d7c-6041585dd421" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_019e2b1c-f606-73c9-a3fe-1ff363cd7774" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_019e2b1c-f606-73c9-a3fe-1ff363cd7774_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_019e2b1c-f606-73c9-a3fe-1ff363cd7774" xlink:to="loc_us-gaap_EquityComponentDomain_019e2b1c-f606-73c9-a3fe-1ff363cd7774_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_019e2b1c-f606-780c-912e-b959e96d18ee" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_019e2b1c-f606-73c9-a3fe-1ff363cd7774" xlink:to="loc_us-gaap_EquityComponentDomain_019e2b1c-f606-780c-912e-b959e96d18ee" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockMember_019e2b1c-f606-78c7-a8d8-b17186818873" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CommonStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_019e2b1c-f606-780c-912e-b959e96d18ee" xlink:to="loc_us-gaap_CommonStockMember_019e2b1c-f606-78c7-a8d8-b17186818873" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_WarrantMember_019e2b1c-f606-7707-93c1-787d52c0b6cd" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_WarrantMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_019e2b1c-f606-780c-912e-b959e96d18ee" xlink:to="loc_us-gaap_WarrantMember_019e2b1c-f606-7707-93c1-787d52c0b6cd" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentType_019e2b1c-f606-7147-8ef1-8f75f2428d25" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_DocumentType"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019e2b1c-f606-731e-bf9b-da867c14245f" xlink:to="loc_dei_DocumentType_019e2b1c-f606-7147-8ef1-8f75f2428d25" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentPeriodEndDate_019e2b1c-f606-7016-ab64-ddbea1fb50e0" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_DocumentPeriodEndDate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019e2b1c-f606-731e-bf9b-da867c14245f" xlink:to="loc_dei_DocumentPeriodEndDate_019e2b1c-f606-7016-ab64-ddbea1fb50e0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityRegistrantName_019e2b1c-f606-781c-a71b-4bafa2fdfda4" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityRegistrantName"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019e2b1c-f606-731e-bf9b-da867c14245f" xlink:to="loc_dei_EntityRegistrantName_019e2b1c-f606-781c-a71b-4bafa2fdfda4" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityIncorporationStateCountryCode_019e2b1c-f606-7a53-bd4f-1ab538e8b9ac" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityIncorporationStateCountryCode"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019e2b1c-f606-731e-bf9b-da867c14245f" xlink:to="loc_dei_EntityIncorporationStateCountryCode_019e2b1c-f606-7a53-bd4f-1ab538e8b9ac" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityFileNumber_019e2b1c-f606-70a1-afd0-19a18153c482" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityFileNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019e2b1c-f606-731e-bf9b-da867c14245f" xlink:to="loc_dei_EntityFileNumber_019e2b1c-f606-70a1-afd0-19a18153c482" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityTaxIdentificationNumber_019e2b1c-f606-7833-bc36-690429e6b524" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityTaxIdentificationNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019e2b1c-f606-731e-bf9b-da867c14245f" xlink:to="loc_dei_EntityTaxIdentificationNumber_019e2b1c-f606-7833-bc36-690429e6b524" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressAddressLine1_019e2b1c-f606-7484-be57-66add5909b98" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityAddressAddressLine1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019e2b1c-f606-731e-bf9b-da867c14245f" xlink:to="loc_dei_EntityAddressAddressLine1_019e2b1c-f606-7484-be57-66add5909b98" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressAddressLine2_019e2b1c-f606-7ac9-b060-547363e13604" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityAddressAddressLine2"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019e2b1c-f606-731e-bf9b-da867c14245f" xlink:to="loc_dei_EntityAddressAddressLine2_019e2b1c-f606-7ac9-b060-547363e13604" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressCityOrTown_019e2b1c-f606-71df-9e76-6cda1c8b64bb" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityAddressCityOrTown"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019e2b1c-f606-731e-bf9b-da867c14245f" xlink:to="loc_dei_EntityAddressCityOrTown_019e2b1c-f606-71df-9e76-6cda1c8b64bb" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressStateOrProvince_019e2b1c-f606-7bb7-9ed0-c9d505ab3b39" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityAddressStateOrProvince"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019e2b1c-f606-731e-bf9b-da867c14245f" xlink:to="loc_dei_EntityAddressStateOrProvince_019e2b1c-f606-7bb7-9ed0-c9d505ab3b39" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressPostalZipCode_019e2b1c-f606-7ab8-a85a-5f4fe026d1bd" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityAddressPostalZipCode"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019e2b1c-f606-731e-bf9b-da867c14245f" xlink:to="loc_dei_EntityAddressPostalZipCode_019e2b1c-f606-7ab8-a85a-5f4fe026d1bd" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_CityAreaCode_019e2b1c-f606-7868-895a-1af8ee496c59" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_CityAreaCode"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019e2b1c-f606-731e-bf9b-da867c14245f" xlink:to="loc_dei_CityAreaCode_019e2b1c-f606-7868-895a-1af8ee496c59" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_LocalPhoneNumber_019e2b1c-f606-7778-96f3-9e2188c261d9" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_LocalPhoneNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019e2b1c-f606-731e-bf9b-da867c14245f" xlink:to="loc_dei_LocalPhoneNumber_019e2b1c-f606-7778-96f3-9e2188c261d9" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_WrittenCommunications_019e2b1c-f606-7d4e-9ec3-b502050e8cd3" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_WrittenCommunications"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019e2b1c-f606-731e-bf9b-da867c14245f" xlink:to="loc_dei_WrittenCommunications_019e2b1c-f606-7d4e-9ec3-b502050e8cd3" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_SolicitingMaterial_019e2b1c-f606-785c-807d-7dea901beb4e" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_SolicitingMaterial"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019e2b1c-f606-731e-bf9b-da867c14245f" xlink:to="loc_dei_SolicitingMaterial_019e2b1c-f606-785c-807d-7dea901beb4e" xlink:type="arc" order="14"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_PreCommencementTenderOffer_019e2b1c-f606-78ea-b875-7ad67eece729" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_PreCommencementTenderOffer"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019e2b1c-f606-731e-bf9b-da867c14245f" xlink:to="loc_dei_PreCommencementTenderOffer_019e2b1c-f606-78ea-b875-7ad67eece729" xlink:type="arc" order="15"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_PreCommencementIssuerTenderOffer_019e2b1c-f606-76c4-8c8c-a8250d98106e" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_PreCommencementIssuerTenderOffer"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019e2b1c-f606-731e-bf9b-da867c14245f" xlink:to="loc_dei_PreCommencementIssuerTenderOffer_019e2b1c-f606-76c4-8c8c-a8250d98106e" xlink:type="arc" order="16"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_Security12bTitle_019e2b1c-f606-7b32-a3e6-b28be5e8f4fe" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_Security12bTitle"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019e2b1c-f606-731e-bf9b-da867c14245f" xlink:to="loc_dei_Security12bTitle_019e2b1c-f606-7b32-a3e6-b28be5e8f4fe" xlink:type="arc" order="17"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_TradingSymbol_019e2b1c-f606-736c-8ae4-6016dbee1fa5" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_TradingSymbol"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019e2b1c-f606-731e-bf9b-da867c14245f" xlink:to="loc_dei_TradingSymbol_019e2b1c-f606-736c-8ae4-6016dbee1fa5" xlink:type="arc" order="18"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_SecurityExchangeName_019e2b1c-f606-7522-a5dc-9c90064eadc4" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_SecurityExchangeName"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019e2b1c-f606-731e-bf9b-da867c14245f" xlink:to="loc_dei_SecurityExchangeName_019e2b1c-f606-7522-a5dc-9c90064eadc4" xlink:type="arc" order="19"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityEmergingGrowthCompany_019e2b1c-f606-752d-947f-e3f7b3952b1c" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityEmergingGrowthCompany"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019e2b1c-f606-731e-bf9b-da867c14245f" xlink:to="loc_dei_EntityEmergingGrowthCompany_019e2b1c-f606-752d-947f-e3f7b3952b1c" xlink:type="arc" order="20"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityExTransitionPeriod_019e2b1c-f606-7477-880b-399744a0c2a9" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityExTransitionPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019e2b1c-f606-731e-bf9b-da867c14245f" xlink:to="loc_dei_EntityExTransitionPeriod_019e2b1c-f606-7477-880b-399744a0c2a9" xlink:type="arc" order="21"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityCentralIndexKey_019e2b1c-f606-71d6-a264-1bd2dd9bf642" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityCentralIndexKey"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019e2b1c-f606-731e-bf9b-da867c14245f" xlink:to="loc_dei_EntityCentralIndexKey_019e2b1c-f606-71d6-a264-1bd2dd9bf642" xlink:type="arc" order="22"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_AmendmentFlag_019e2b1c-f606-7fbc-bee9-52d2c46c79c7" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_AmendmentFlag"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019e2b1c-f606-731e-bf9b-da867c14245f" xlink:to="loc_dei_AmendmentFlag_019e2b1c-f606-7fbc-bee9-52d2c46c79c7" xlink:type="arc" order="23"/>
  </link:definitionLink>
</link:linkbase>
