Phantom Spank

the process of masturbating immediately after your hand/arm has become numb either naturally, from a shot, or from sitting on your hand on purpose. Its main purpose is to make it feel like you're not jacking off by yourself in a dark room watching a porno that you've already seen dozens of times.

Also mentioned on the Comedy Central tv show, "Ugly Americans"

when a man saws off his arm and then uses said arm to masterbate to lizzy mcguire