The sexual act between two men, where one man takes his flaccid penis and wraps it around the other man's erect penis in the fashion of a noose around a neck. The man with the noose then proceeds to pleasure the other deviant, and therefore becomes the hangman.
Also its like a favour for a straight guy to do for a gay guy after the gay guy saves his life.
They totally hangman eachother in prison.
Hey did you hear Jimmy actually hangman (ed) Steve last night.