Definitions for "undocumented"
Features included in a program that were not described in the users manual. Sometimes undocumented items are left out unintentionally. Sometimes undocumented features were present to facilitate the writing of the program by the designers and programmers and thought to be unimportant to the end-user. Other times, such features are present as part of a test in determining whether they will be included in future versions of the program.
lacking necessary documents (as for e.g. permission to live or work in a country); "undocumented aliens"; "undocumented tax deductions"