Kook (noun)

A person who is eccentric or unusual in their behavior or beliefs; a peculiar or odd individual.

Origin:

Of uncertain origin, first recorded in the early 20th century, possibly from a british dialect term meaning "madman" or "simpleton".

Examples:

1. He thought the conspiracy theorist was a kook.
2. She was considered a kook by her classmates for her strange fashion choices.
3. The new neighbor was a kook and no one wanted to talk to him.
4. He was always considered a kook because of his unorthodox ideas.
5. The kook was known for his eccentric behavior.