Moron (noun)

1. A person who is notably stupid or lacking in intelligence.
2. A person who is uneducated or lacking in knowledge in a certain field.

Origin:

Derived from the greek word "moros" meaning "foolish" or "dull", first coined by psychologist henry h. goddard in 1910.

Examples:

1. The interviewer was taken aback by the moron's complete lack of knowledge of current events.
2. He was such a moron that he couldn't even spell his own name.
3. The science teacher was getting fed up with the moron who kept asking the same question.
4. He was a complete moron when it came to understanding how the stock market worked.
5. She was convinced that the moron in the corner would never amount to anything.