Definition of "fastball" in English

noun

1. A high-speed pitch of a baseball.

2. (specifically) A four-seam fastball, which is a backspin pitch thrown with a ball gripped in the direction to cause four of the seams of the ball to cross the flight path and released with roughly equal pressure by the index and middle fingers

   • The pitcher had a blazing fastball.

verb

1. (transitive) To throw (something) at a high speed.