1. a. Any of various games, such as baseball, played with a ball.
b. A game with religious and political significance in some pre-Columbian societies of Mesoamerica, southwestern North America, and the Caribbean, played with a rubber ball in a walled court.
2. Slang a. A competition: "But in the winner-take-all world of politics, the contest for the undecided 2 or 3 percent can be the whole ballgame" (Brad Edmondson).
b. A particular condition, situation, or set of circumstances.