A Mushroom is when you dip your cock in paint or ink, And slap someone in the face with it when they are passed out. Thus leaving a mushroom imprint on their face.
"At this party last night, Kim was the first to pass out, So I gave her a mushroom"
A mushroom is an enormous/fat human being with a head shaped slightly abnormal, and a hairstyle which seems to differ from others and resembles a particular type of fungus/mushroom,and their nose seems to be physically misplaced and gigantic.(sometimes it may seem slightly crooked)