The word undocumented refers to something that is not officially recorded or recognized. There are several synonyms that can be used interchangeably depending on the context, including unrecorded, unregistered, unacknowledged, and undocumented. Other words that fall under the same category include illegal, clandestine, and unauthorized. These terms can be used to describe various situations, including the presence of individuals who do not have legal documentation, financial transactions that are not recorded, and goods that are not logged in inventory. Using synonyms for the word undocumented can help communicate complex ideas more effectively and accurately.