The term 'catcher of a fly' can be summarized as a MITT, which is a four-letter word. A MITT is a type of glove used in baseball and softball to catch the ball when it is thrown or hit by the batter. It is usually made of leather or other materials and has webbing between the thumb and forefinger to help the player grip the ball. The MITT is worn on the hand of the defensive player, usually the catcher, who stands behind home plate and catches the ball when it is thrown by the pitcher.