Definition from Wiktionary, the free dictionary
curveball (plural curveballs)
- (baseball) A forespin pitch thrown by rotating the index and middle fingers down and resulting in motion down "curve"
- He bit on a curveball in the dirt.
- (by extension) An unexpected turn of events initiated by an opponent or chance.
- Life has thrown him a few curveballs.
- (baseball): fastball, hardball, slider, cut fastball, two-seam fastball, split-finger fastball, sinker, screwball, softball, knuckleball
unexpected turn of events
- (baseball) To throw a curveball.