Verb: An act occurring after anal intercourse, where the man removes his "Mushroom"-headed warrior from his female participant's rectum or balloon knot, and proceeds to take his poo-stained man-pole, and slaps his partner in the face or forehead (whatever preferred), leaving a mark (or stamp) in the shape of the tip of the distributor's dong (mushroom-esque);
> When I was finished penetrating her poop shoot, I used her rectal leftovers to give her a Mushrrom Stamp