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.
Your extremely constipated all day and in a location where dropping this enourmous stinkloaf would be innappropriate so you decided to wait until you return to your own throne. After you squat and relieve your stomach of the huge bodily mass that has been baking in your belly all day, you come to find that your left with a raging woody from the state of euphoria you have achieved. Choosing what you do with the chubby is your own preference.
Beau: Oh man, I had to hold that dump in all day, I couldnt drop that turd at work. But boy oh boy was it relieving.
Sam: Want me to finish off your dirty diamond steel, I see your pitchin a little tent in your gym shorts there.