Knuckleball

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 lack of spin causes vortices over the stitched seams of the baseball during its trajectory, which in turn can cause the pitch to change direction – and even corkscrew – in mid-flight. 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, since following the path of the ball makes it difficult to call balls and strikes.