When you smash the end of your cock against the face of a deserving party(preferbably with your man berries resting in their best friends mouth) and leave the impring of a mushroom behind to show who's king.

a mushroom tattoo is when one of the male sex whips out his extremely large penis and whips u any where on the facial region. if enough force is applied a red bruise from the tip of the penis will appear on the face in the shape of a mushroom..hence the name mushroom tattoo.

A mark made by a wild and violent whipping/smacking of the male genitalia on another's body part, preferably tha face.

in agreeance with the above definitions, a 'mushroom tattoo' is a result of the under-side of the head of a man's penis having been quickly and force-fully applied to the fore-head of another person (preferrably a female). said to have originated by accident when some over-zealous young man, in an attempt to ejaculate in a more timely fashion, masturbated while being blown - the penis came out of the females mouth and, on the down-stroke, struck her fore-head, thus leaving a bruise of sorts in a shape some-what resembling a mushroom. also, upon occassion, used in by those persons leading a bdsm life-style to mark a slave or sex-toy. WARNING - not recommended! can be very painful for BOTH parties involved...

See mushroom stamp

To smack someone in the face with a cock

To slap someone in the face with the tip of your dick, hard enough to leave a mark of the head of your dick.