Short for role play. Typically for games.
But nowadays teenagers "RP" someone so they take some random persons face from Tumblr or instagram and pretend to be that person.
saying to a girl that's nasty, self centered
a total bitch, or stanks
shell never no what your sayin!
*girl walks bye*
Rich: dammmnn girrl clean that RP of yours...I'm dyin over here
Jen: RP whachu talkin bout?
Rich: Rank Pussy Jen that's you....RP.
Jen: uhhhh