Definition of knuckleball in US English:

knuckleball

(also knuckler)

noun

Baseball
  • A slow pitch that has virtually no spin and moves erratically, typically made by releasing the ball from between the thumb and the knuckles of the first joints of the index and middle finger.

    • ‘Wilhelm and Niekro are the only two pitchers in the Hall of Fame who relied primarily on the knuckleball throughout their careers.’
    • ‘Eddie Cicotte is thought to be the first major league pitcher to specialize in throwing the knuckleball.’
    • ‘He had pitched in high school and occasionally had thrown a knuckleball.’
    • ‘Sauveur throws a fastball, knuckleball, curveball and cutter, and he changes speeds with all of them.’
    • ‘You'll learn the rules of offense and defense, and all about fastballs, curveballs, knuckleballs and screwballs.’

Pronunciation

knuckleball

/ˈnəkəlˌbôl/