Dickhead

Def. 1) A terrible condition that affects most of the people you will ever meet causing a penis to grow off of said person's forehead.

Def. 2) That kid in your science class that deliberately failed all his tests making him "cool".
Def. 3) Your Boss and most of your colleagues.

Doctor: Sir, I'm afraid you suffer from Dickhead Syndrome.
Your Boss: Is it bad?
Doctor: It's the most severe case that I've ever seen. It is possibly fatal.