← BackshareGuessknuckleheaded/ˈnʌkəlˌhɛdɪd/adjectiveStupid or foolish; showing a lack of good sense.She regretted her knuckleheaded behavior at the party.That was a knuckleheaded thing to say during the meeting.His knuckleheaded decision to skip class got him in trouble.SynonymsfoolishstupidAntonymssensible