A baseball term referring to the achievement by a pitcher of recording all three outs in an inning via the strikeout.
The "side" is a term used to refer to the batters who appear for the offensive team during their half of the inning. When the defensive team records the third out of the inning, the side is "retired." While a pitcher can strike out three consecutive batters to strike out the side, this is usually referred to as "striking out the side in order." Although there is some disagreement on the subject, the pitcher can surrender any number of hits in an inning and still record all three outs as strikeouts to strike out the side.