shadow system
term used in information services for any application relied upon for business processes that is not under the jurisdiction of a centralized information systems department.
en-US/ˈʃæˌdoʊ ˈsɪstəm/
en-GB/ˈʃædəʊ ˈsɪstəm/
term used in information services for any application relied upon for business processes that is not under the jurisdiction of a centralized information systems department.