Dirty Santa is a game played at Christmas, kind of like a White Elephant Gift Exchange, or a Yankee Swap I think I've heard it called? Basically, everyone brings a wrapped gift, then each person draws a number (or goes in order of age, at my grandparents' house) and then takes turns either opening a wrapped gift or stealing a gift that a person has already opened. There are different variations and rules, but that's the gist of it. They're a ton of fun!