To masturbate with such a tight grip on one's penis that it is denied the oxygen it requires to function properly. Much like in a cartoon, the head turns blue over time. A two-handed grip is used, and it is an extrememely intense action to observe.
Mother: Billy, time for dinner!
Billy: NO!! I'm stangulating.
Mother: Hmm? What does strangulate mean?
Billy: Nothing, keep the door closed please!