A slight
shake of the head, meaning you screwed up so
bad, that the other side can only
shake their head. Or, other side is fed up with your shit.
Example 1:
Bob: DUDE! I ate a porcupine -- when it was still ALIVE!
Freddy: *Shake of the head*
Example 2:
Bob: Dude, I climbed Mt. Everest, pulled of my
helmet, para-glided down, and landed on my head! And the only evidence I have is this small scratch on my elbow!
Freddy: *Shake of the head*