This is where you deprive your brain of oxygen while rubbing one out.
IMHO, this is perhaps one of the stupidest ways to get your jollies, but hey, people do it.
According to Wikipedia, upwards of a thousand people die annually from this, though that number could be understated because when friends and family find you, they clean up the evidence as suicide is preferable to telling the world you were a perverted freak.
So, who does this?