Basketballing is a sexual act in which a male takes his testicles and forces them into the anus of their sexual partner. There are several variations: gay or straight, dribbling, slam dunking, etc. Very popular among those who enjoy kinky sex.
John: That bitch Jennifer has a sweet ass
Kyle: Yeah I would really like to shove my balls up that and give her a taste of 'the boys'
John: Totally. I would basketball her in a heartbeat.