The act of sitting on one's hand for 20 minutes to make it go numb, and proceeding to jerk off with that hand. This will give the feeling of a hand job from someone else.

Sitting on your hand until it is numb, then proceed to rub one out.

From Chapelle Show:
To masturbate while you hands are numb, to give the sensation that someone else is pleasuring you.

When you sit on your hand until it becomes numb, then masturbate.

Sitting on your hand until it falls asleep and then jerking off, giving you the feeling of a hand job from someone else.

When one sits on ones hands until there are numb and then jerks off. This will feel like a job from someone else, hence the name, "the stranger"
Derivatives:
Mr. Freeze - stick joor hand in icewater until it is numb and proceed
The Snowman - stick your hand in snow and proceed
Pyro - Burn your hand until you cant feel it and proceed

aka "The Stranger"
The act of sitting on your hand until it falls asleep, then rubbing one out so it feels like someone else is doing the deed.