1. A learned person or someone who knows a great amount about a particular subject: Rhonda is really a computer savant because she is an excellent authority regarding computers.
2. Someone who does not have normal intelligence but who has a very unusual mental ability that other people do not have: Michael had poor reading skills; however, he was considered a savant because he could do unbelievable things with numbers and he had a fantastic memory of historical facts.

Savant is now the preferred term for "idiot savant" and is recommended as the word which should be used instead.

An intellectually disabled person who exhibits extraordinary ability in a highly specialized area; such as, mathematics or music: Idiot savant is no longer considered an acceptable term and "savant" is now the preferred reference for this definition.

A foolish or stupid person: Kyle felt that he really made an idiot of himself at the dinner table the other night by asking the hostess an embarrassing question by mistake!

An idiot driver kept trying to pass Joel on the narrow road the other night while he was going at the speed limit while other cars were coming from the opposite direction.