An acronym for "Parking Lot Action". Pronounced "play". It is the act of having sex in an establishment's parking lot. Getting your smash on in the parking lot. Gettin some play in the parking lot. Usually when heavily intoxicated, one will pick-up a stranger at a bar and have sex in the parking lot vs. having the other person find out where they live.
It can also be used as an adjective to describe a female who looks as if she has the potential to perform dastardly deeds in the parking lot.