1 definition by Crank Johnson
A "Crimson Mushroom" is given to an unsuspecting person by removing one's flaccid penis from one's trousers and slapping said penis across the cheek, forehead, eye socket or other impressionable area of the body (preferably the face) so as to cause a large, red, mushroom shaped outline on the recipient.
by Crank Johnson July 18, 2008