Curveball

Noun

 * 1)  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.
 * 1) An unexpected turn of events initiated by an opponent or chance.
 * Life has thrown him a few curveballs.

Coordinate terms

 * fastball, hardball, slider, cut fastball, two-seam fastball, split finger fastball, sinker, screwball, softball, knuckleball