A game, usually in basketball, that starts spontaneously by a group of random people or with friends. There aren't any refs or officiating, and the calls are all on the players, which can get a little unfair and annoying depending on who you play with. The players pick the teams and rules.
*Jack and John shooting around at the court, while Guy 1 and Guy 2 are doing the same on another court*
Jack- Hey, you think we can take those two guys? Let have a 2-on-2 pick-up game with them.
John- I dunno, Guy 1 is 7 feet muscular and black, and Guy 2 is fat, hairy, sweaty, and shirtless. I better not post him up.
Jack- alright then, I call Guy 1, and you'll got Guy 2. We're going up to 21, win by 2, make it take it.