Commonly abbreviated PBR, is the he act of swiftly rubbing/ brushing your unexposed penis against a woman's buttocks as you are making the impression that you are "squeezing through" to get by in a crowded group of individuals, generally at a social event; ergo middle school dance, redeeming the pleasure of simply having your penis rub up against an ass. If the victim of PBR catches you red handed, you will ultimately face a night of embarrassment, for you were unsuccessful in fulfilling your ass-dwelling fantasies.
"Wow this party sucks, nothing but a bunch of prudes. Alas, a good Penis Butt Rub will suffice."
Person 1: "Hey man, you going to Chester's party on saturday?"
Person 2: "Will there be...PBR? If so, you can count me in!!"
Person 1: "Uhhh dude i dont know... besides that beer is for hipsters."
Person 2: "No not Pabst Blue Ribbon..Penis Butt Rub"