The knuckleball is a baseball pitch that has very little spin, causing it to flutter erratically on its way to the plate. This makes it very difficult for batters to hit, as they cannot predict where the ball will go.
Knuckleballs are thrown with a loose grip, and the pitcher does not impart any spin on the ball. The ball is released with the knuckles of the index and middle fingers, and the lack of spin causes the ball to wobble and flutter as it travels through the air.