an inconspicuous clause in a document or bill that affects its meaning in a way that is not immediately apparent
"when I demanded my money he showed me the joker in the contract"
a playing card that is usually printed with a picture of a jester
"The dealer pulled the joker from the deck to complete his hand of five cards."
A person who makes jokes.
"The class clown, known as our favorite joker, always had everyone laughing during lunch breaks."
A fictional villain of DC Comics, noted for his insanity and cunning, who either wears clown makeup or is disfigured to appear as such, and who is archenemy of Batman.
"After years of battling the Joker in Gotham City, Batman finally realized that no amount of detective work could stop a villain driven purely by chaos."