← BackshareGuessknucklehead/ˈnʌkəlˌhɛd/nounA stupid or foolish person.That knucklehead forgot his keys again and locked himself out.My little brother is a knucklehead who never listens to advice.Don't be such a knucklehead; you need to think before you act.SynonymsdummyfoolblockheadAntonymsgenius