Someone who is extremely smart but who acts like a ditz. he or she may also be described as "smitzy".
See that girl? You'd never guess by looking at her that she's super smart, because she acts like a ditz. She's really a smitz.
My boyfriend is President of the Chess Club and was accepted to Harvard. But he's forever losing his phone, locking himself out of his car, and leaving his wallet at home. He's such a smitz.
My nickname is Smitzy, because people know I'm a smitz.
One who receives it up the butt
up yours, ohh wait its already been taken