A checked swing is a type of motion in baseball made by a batter. A checked swing occurs when a batter starts to swing his bat at the ball, but stops the swing in order to allow the ball to pass without hitting it. If the swing was indeed checked, so that there was actually no swing, then if the bat did not touch the ball and if the ball did not go through the strike zone, the pitch counts as a ball; but in that circumstance if the swing was not checked, so that a swing actually occurred, then the pitch counts as a strike.
Initially, the home plate umpire must determine if a swing was checked or not checked. If he indicates that it was checked, an appeal can be made by the catcher or his manager, and the home plate umpire can then make a request to either the 1st or 3rd base umpire to make the call as to whether or not the swing was indeed checked. (To maximize visibility, the 1st base umpire makes the call for right-handed batters, and the 3rd base umpire for left-handed batters.) To indicate a checked swing, the umpire will make a “safe” gesture with his hands; to indicate a full swing, he will clench his fist.
If a ball that passes the batter goes through the strike zone, it is a strike even if a swing is checked. A checked swing sometimes results in an unintentional swinging bunt, where the ball hits the bat and rolls a short distance, although the batter apparently stopped his swing. If a ball is hit during a checked swing, it is in play as long as it is not ruled a foul ball.
The Major League Baseball rulebook does not contain an official definition for a checked swing, merely stating that a swing either does or does not occur; it is the decision of the umpire as to which is the case. Generally, factors such as whether the bat passes the front of the plate or the batter pulls his wrists back are