1 definition by The Rascal King
To mushroom is to, when singing along to a song, either mumble or sing the wrong words, revealing that you don't really know how the song goes. When someone does this, everyone around them yells "MUSHROOM!" at them, as a way to embarrass them.
Matt: If you wanna be my lover, you have got to give....doo doo doo...but that's the way it is!!
Nick: Oh Matt, you totally just Mushroomed!
Everyone in car: MUSH-ROOM! MUSH-ROOM!
Nick: Oh Matt, you totally just Mushroomed!
Everyone in car: MUSH-ROOM! MUSH-ROOM!
by The Rascal King October 31, 2007