Idiot definition: an utterly foolish or senseless person.. See examples of IDIOT used in a sentence. The meaning of IDIOT is a foolish or stupid person. How to use idiot in a sentence. Idiot Has Greek Roots Usage of Idiot : Usage Guide 2 meanings: 1. a foolish or senseless person 2. old-fashioned, offensive a person with a severe learning disability.... Click for more definitions. Idiot vs. Stupid What's the Difference? Idiot and stupid are both derogatory terms used to describe someone who lacks intelligence or common sense. However, idiot is often seen as a more severe insult, implying a lack of mental capacity or understanding, while stupid is more commonly used to describe someone who makes careless or foolish decisions. Both terms are considered offensive and should be used with caution to avoid causing harm or offense to others. Copy This URL Comparison