if someone happens to be getting fresh with you, mushroomslap them. This means pulling out your jimmy and making solid contact with their facial region.
C-dav definitely mushroom slapped that girl last period because she said "oh my gosh guys guess what happened?"
When a guy takes his hard dick, and swings it as hard as he can, hitting a person (hopefully a girl) on her body with his mushroom. If done correctly it will leave a mushroom imprint for several minutes with a lasting red spot afterwards.
(not easy to do)
ex) mushroom slap her in the face and it will leave a mark. very funny. total ownage
"Ben gave me an Intergallactic Mushroom Slap. Because he's on parole the government is footing the cosmetic surgery bill, so hopefully I'll be able to laugh about it in years to come."