Plain English Meaning
An approach to a runway that is flown using GPS only, with its own dedicated chart. It is not a GPS version of an existing ground-based approach -- it is a procedure that exists on its own.
Full Definition
An instrument approach procedure built entirely around area navigation using GPS as the primary navigation source, designed independently of any ground-based navigation aid. The procedure is published on its own approach chart titled 'RNAV (GPS) RWY XX' and does not overlay or share course guidance with a VOR, NDB, ILS, or localizer procedure to the same runway.