Much like the ever-popular circle jerk, the slam circle involves a group of young males assembled in ring formation. They then reach to their immediate right, and proceed to whack off the guy next to them. In the middle of the ring, there is a small bucket that collects all the semen. The last to ejaculate (loser) must drink the contents of said bucket.
Frank: Hey im going over to Tommy's frat tonight, want to come?
Joe: No way man! All they do there is start Slam Circles!
Frank: You just don't want to go because you always lose!