Tripwire

Part of speech: noun

Definitions

1. A device set up so that when its wire or line is touched or moved, it activates an alarm or explosive mechanism
2. An arrangement using a taut wire or string that, when tripped, causes a signal or detonation to occur
3. A trigger mechanism consisting of a stretched wire that initiates a response upon being disturbed

Etymology: "Tripwire" is about as transparent as compounds get: "trip," to catch a foot or cause a stumble, joined to "wire," the thin metal line. The image is literal. A taut strand stretched across a path catches a passing foot, and the trip sets something off. The term is used for both the military booby trap and the household alarm wire that rings a bell or switches on a light when disturbed. What makes the word worth a second look is how little it has changed. "Trip" once meant to make someone stumble, and "wire" once meant a drawn metal thread, so the compound describes its mechanism without metaphor. Nothing about the word has drifted far from its parts, which is unusual for a term that now covers everything from a garden alarm to a battlefield device.

Synonyms: detector, trigger, alarm, wire, safety

Antonyms: safety, protection, security, safeguard, prevent