Puzzle Head 

Someone that looks normal at first glance and appears to be a fully functioning human being, but in fact suffers from a severe mental illness or retardation.
Insinuates that the inside of someones head is like an unsolved puzzle and does not function correctly.

-Shit! that guy is petting that ladies dog WAY TOO HARD! whats his deal?

-Puzzle head bro, doesn't even know its a dog"

Puzzle Head by the throwdown August 17, 2010

Puzzle Piece Head 

When one's hair is receding on the sides, creating a perfect puzzle piece

Look at John's puzzle piece head, I think he stole the last piece of my puzzle and inserted it into his hairline.

Puzzle Piece Head by DeeDee11 September 28, 2011