Plain English Meaning
A code pilots write on a flight plan to tell air traffic control what's on the aircraft. /TP means the aircraft has a transponder that reports altitude, but it does not have GPS or other area navigation gear.
Full Definition
An ICAO/FAA flight plan equipment suffix indicating the aircraft is equipped with a transponder that has Mode C (altitude reporting) capability but does not have area navigation (RNAV) equipment on board.
Context Anchor
Seen in coded pilot weather reports, where each slash mark introduces a different part of the report.