Boob/buːb/ Definition 1 of 3Pro Tip 1/3Colloquially Insulting Used informally to insult someone's intelligence in a light-hearted way. He's such a boob, always forgetting his keys. Pro Tip 2/3Not for Formal Use Avoid using 'boob' in professional or formal settings, it's too casual. I wouldn't call my boss a boob, even as a joke. Pro Tip 3/3Gender Neutral This insult doesn't target a specific gender, can refer to any silly person. My sister acted like a boob when she lost her ticket.