(baseball) A forespin pitch thrown by rotating the index and middle fingers down and resulting in motion down "curve" / (by extension) An unexpected turn of events initiated by an opponent or chance.

(baseball) To throw a curveball.

plural of curveball

simple past tense and past participle of curveball

present participle of curveball

plural of curveballer

(baseball) A player who throws curveballs.