Joker

The joker is a special card that is most often used as a wild card or a limited wild card (aka a bug).

An American 19th-century invention, the joker is the newest addition to the standard card deck. Because their rulesets had been developed before the introduction and popularization of the joker, most traditional card games (such as blackjack and poker) do not use this card. 

Fun gambling fact:

Despite its name, a standard 52-card deck actually contains 54 cards. This is because it comes with two jokers, which are not counted as part of the total.

Joker:

• A special card that is most often used as a wild card or a limited wild card.