← BackshareGuessninnyhammer/ˈnɪniˌhæmər/nounA foolish or naive person; a simpleton.He called his friend a ninnyhammer for losing the keys again.The old tale warned children not to be ninnyhammers and trust strangers.Only a ninnyhammer would believe that ridiculous story.SynonymsninnyfoolsimpletonAntonymsgenius