To take a sac of beans, preferably in a sock, and insert it into your urethra. Works on woman and men, but the term is generally used on gay men. It is not for pleasure in any way, it is meant as torture. However, if your mind is messed up enough, it could be used as a way to reach orgasmic climax.
"Hey did you just see Tim? I heard he got Bean Fucked!"
"Is that why he was walking around the party all sad and grabbing his shaft in pain?"
"I bet so..."