joker

noun12

1. •
   A person who makes jokes.
2. •
   (slang) A funny person.
3. •
   A playing card that features a picture of a joker (that is, a jester) and that may be used as a wild card in some card games.
4. •
   An unspecified, vaguely disreputable person.

   • Some joker keeps throwing eggs at my windows.
5. •
   A loser.

   • Don't waste your breath on these jokers round here.
6. •
   The option, in a pub quiz, of selecting one particular round in which one's team will score double points.

   • We used our joker as soon as the topic of sports was announced, since we are sport experts.
7. •
   (figurative) Something kept in reserve that can be used to gain an advantage; a trump card.

   • Rebus decided to use their joker. 'Mr Lintz made a phone call to this office. He was talking for over twenty minutes.' — 2008
8. •
   A jester.
9. •
   (New-Zealand, informal) A man.
10. •
    A clause in a contract that undermines its apparent provisions.

    • Discussion of contracts and the many provisions contained therein led to a vote making it the sense of the convention that manufacturers should use a simple sales contract, free from jokers. — 1922
11. •
    A fairy chess piece that moves like the last piece that was moved by the opponent.
12. •
    A friendly unit that acts as a suspected hostile unit in a military excercise.

    • Joker - A friendly track or contact acting as a "suspect" track for exercise purposes only. (STANAG 1241) — 1998