A batter is said to have struck out swinging when he makes an attempt at a pitch and does not make contact with the ball, or fouls the ball directly into the catcher's mitt. The batter's bat must make sufficient forward progress to be ruled a genuine swing. It should be noted that if there are fewer than two outs and no runner on first base, a batter can strike out swinging and still make it to first base if the catcher does not catch the ball cleanly and is not able to retrieve the ball and throw to first base before the batter reaches it.
Batters strike out swinging either because they have missed a good pitch in the strike zone or they swing at a pitch that they cannot reach and is usually out of the strike zone. Controversy sometimes erupts when a batter takes an abbreviated swing at a pitch that would be the third strike and is ruled to have made a genuine attempt at the ball, thus striking out. Many times, the first-base or third-base umpire (depending on whether the batter is left- or right-handed) is asked to make a ruling on such checked swings to determine if the batter went around and thus struck out. Just because a batter strikes out swinging does not necessarily end the play. If no one is on first base and there are fewer than two outs, the batter can run after striking out if the catcher has not fielded the ball cleanly. Many batters do advance to first base in such situations, although the pitcher is still credited with a strikeout. in this way, pitchers have struck out more than three batters in an inning.