Disgusting variation of the regular pulloff, aka toss, wank, jerk, etc., but involving dirty hands. Usually, but not always, done to an unsuspecting victim.
Craig got way too drunk on a Sunday morning drinking bottomless mimosas. He was horny, but his girlfriend Kristine wouldn't let him fuck her and kicked him out of the house. He passed out in the local park and woke up with his pants undone getting a a dirty pulloff from some homeless man.