The act of stimulating the anus by excreting
feces partially out of one's own
ass, then allowing the natural pressure of the anus to
suck the feces back into one's own rectum. The process is repeated to one's satisfaction.
Dude1: So I've been trying out assturdbation lately.
Dude2: Oh man, I tried that once, it didn't
work for me.
Too much leakage.
Dude1: Yeah man, you've got to
change your diet to avoid all types of fiber.