What is "knuckleball"

also knuckle-ball, baseball pitch, by 1909, from knuckle (n.) + ball (n.1). So called from the position of the fingers in throwing it. Related: Knuckleballer.

n. 1 (context baseball English) A pitch thrown with the ball gripped on the fingertips and released with no rotation which travels over an unpredictable path to the plate due to micro-turbulence in the air. 2 An event that is hard to predict. vb. (context intransitive baseball English) To pitch knuckleballs.

n. a baseball pitch thrown with little speed or spin [syn: knuckler]

A knuckleball or knuckler is a baseball pitch thrown so as to minimize the spin of the ball in flight, causing an erratic, unpredictable motion. The air flow over a seam of the ball causes the ball to transition from laminar to turbulent flow. This transition adds a deflecting force on the side of the baseball. This makes the pitch difficult for batters to hit, but also difficult for pitchers to control and catchers to catch; umpires are challenged as well, as the ball's irregular motion through the air makes it harder to call balls and strikes.