A baseball term defined by the success of the defensive team at recording three outs against the opposing team's batters in an inning (not necessarily consecutively).
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." Many pitchers strive to "strike out the side", meaning they have recorded all three outs in an inning by way of the strikeout, although this can occur even if they have given up hits to other batters in the same inning. If the side is "retired in order", this means the defensive team has recorded three consecutive outs from the beginning of the inning. This is also referred to as a "one-two-three inning."