1. n. the testicles. (Usually objectionable.) He got hit in the balls in the football game.
2. exclam. of disbelief. (Usually an exclamation: Balls! Usually objectionable.) Out of gas! Balls! I just filled it up!
3. n. courage; bravado. (Usually refers to a male, but occasionally refers to female. Usually objectionable.) He doesn’t have enough balls to do that!