Acronym for "peanut butter pie". Riding a stolen vehicle through large puddles of mud (thus resembling peanut butter), generally in empty urban spaces (alleys, beneath bridges, etc.), then smoking marijuana in the vehicle with the windows open, forming white smoke clouds that resemble whipped cream. Often, other snack foods are involved (to tend to the post-high munchies), such as chips or candy.
Steve: Hey man, you want to go to the opera tonight?
Ronald: Naw, let's go PBP instead!
Steve: Good thinking! I still have Pringles and jolly ranchers left over from last time!