Deuce is gambling slang for the number two. You will hear it in everyday speech too, but casinos use it in several specific ways.
In card games, a deuce is any card ranked two, so a pair of twos is “a pair of deuces”. In video poker, games such as Deuces Wild turn every two into a wild card. In dice games, a deuce is a total of two, which can only be thrown as two ones, better known as snake eyes. The context — cards or dice — always tells you which meaning a player has in mind.
Deuces in video poker
Video poker variants built on wild deuces are a staple of the category, but their paytables vary widely from one version to another. Compare the return figures before you add a variant to the lobby, just as you would for Jacks or Better.