While a native version of GTA V was never released for the PlayStation Portable (PSP), creative modders use the PSP's existing engine to build "remakes" or "re-skins" of older titles like GTA: Vice City Stories or Liberty City Stories to resemble the modern Los Santos environment.
This specific keyword typically points toward a "Highly Compressed" version of a GTA V mod.
: Only download from reputable community sites. Official GTA V downloads should be done via Steam or the Rockstar Games Launcher for PC.