A weapon worn at the side of the body, especially a pistol or sword; or in baseball, a throwing motion from the side.
From 'side' + 'arm' (weapon). The compound word emerged in military terminology for weapons worn on the hip or waist, and later adopted in baseball.
Sidearm throws in baseball are trickier for batters because they come from an unexpected angle—it's one of those words where the literal meaning (weapon at your side) inspired a baseball technique.
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