A missile or weapon system designed to detect and destroy incoming enemy missiles in mid-flight.
From counter- (against) + missile (from Latin missilis, 'that may be thrown'). This modern military term emerged during the Cold War as nations developed air defense systems.
Air defense systems like the Patriot missile were actually countermissiles—designed to shoot down other missiles—which meant winning a dogfight between unmanned weapons traveling faster than sound.
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