A mental handicapped person (or window licker ). They wear bright luminous crash helmets so they are easily recognisable and do not stray too far from their spaz wagon. Helmet also helps in event of multiple spasms, fits or collisions with lamp posts.
"Hey Johnny, look at those helmet heads chasing the ducks."
A hair cut that forms a perfect "helmet" shape around the head itself. Many times this can be accomplished by a horrible haircut and lack of caring in the morning tossed with a side of being a boner. This non-trendy look is usually seen on people with the name "Mike".
"Man, Mike walked in this morning with some crazy helmet head! Die it pink and he'd look like a penis!!"