Joker (noun)

1. A person who is fond of joking and making witticisms; a jester.
2. A playing card with a picture of a jester, which is often wild in games.
3. A person who does not take things seriously and does not adhere to the rules.

Origin:

From the middle english word "jokere" meaning "a jester".

Examples:

1. He was the class joker and always had a witty remark.
2. The joker card can be used as any card in the deck.
3. He played the joker and refused to follow the plan.
4. The joker was always making jokes and never seemed to be serious.
5. He was called a joker because he didn't take anything seriously.