Just like wrestling, except both men are naked and have erections. The objective is to insert your penis into the other man's anal hole without having him insert his into yours.
Guy 1: I'm starting a rape battle club in my basement.
Guy 2: That's sick!
Guy 1: I'm going to teach people rape techniques.
Guy 2: Like what?
Guy 1: Like clenching your butthole to block the other guy's dick.