joker

A joker is a special card that has a picture of a joker (or jester) and can take any value in certain card games.

A joker is a person who makes lots of jokes.

A joker refers to a funny person.

A joker is also known as a jester.

A joker refers to a person that is not known, but has a bad reputation and name.

Example: There is some joker around here that keeps knocking on my door but does not appear.