Lit., "fucking knucklehead" Usually reserved for someone who stubbornly adheres to false principles or consistently acts irresponsibly; generally, an idiot.
"She hates your guts, you fucklehead! Quit calling her!"
When you fail at something in life (eg. failing an exam or not getting a job), go home and spend an hour just standing in the shower, propping yourself up against the wall with your eyes on your feet.
Caleb knew the only thing to do after he didnt get prefect was take a failureshower.