When your parents are home or you're too cheap to buy a motel room, you and your bitch fuck in your car, hence car fucking. Usually, the man will sit in the back seat while the girl sits on him and rides his dick.
Joe: Did you and that whore go back to your place?
Dave: Fuck no, my mom was home, so i fucked her in my car.
Joe: Ha. You went car fucking
Dave: Fuck yeah.