A fork of Rural Dictionary
When a a dude and chick have anal sex and when the guy pulls out, poop is on his dick and he slaps the girl on the cheek with his dick removing all of the poop on his dick and leaving it on her face in the shape of a mushroom.
Jamie: "Dude, David's mushroom stamps hurt!! He hits you so hard with his cock!"
Vanessa: "I like to take a Mushroom Stamp on the tounge."