A baseball glove or mitt is a large glove worn by baseball players of the defending team, which assists players in catching and fielding balls hit by a batter or thrown by a teammate. Gloves are traditionally made of leather; but today other options exist, such as PVC and synthetic leather.

A knuckleball or knuckler is a baseball pitch thrown 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 change from laminar to turbulent flow. This change adds a deflecting force to the baseball, making it 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. A pitcher who throws knuckleballs is known as a knuckleballer.