joker

Noun

Singular joker

Plural jokers

1. (poker cards) A joker is a special card that has a picture of a joker (or jester) and can take any value in certain card games.
2. A joker is a person who makes lots of jokes.
3. (slang) A joker refers to a funny person.
4. A joker is also known as a jester.
5. A joker refers to a person that is not known, but has a bad reputation and name.

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