The process of, while penetrating a partner from behind (Either anally or vaginally), reaching around and playing with his/her genitalia.
Contrary to popular belief, not only a homosexual act.

When your partner gives you a handjob from behind.

That service one provides while fucking you up the ass.

A driving maneuver where a tail-gater moves from left to right to ensure he/she is visible in all of your mirrors.

a homesexual activity in which the person doing them gives them a handjob

The act during a MMF threesome in which a man reaches around another man in a Mitchell-like maneuver and grabs the other man's penis.

A game that wich only man can play. Where you throw a ball is throw'in behind your back to another person. Quit like the flow of atoms.