From Longman Dictionary of Contemporary Englishtripwiretrip‧wire /ˈtrɪpˌwaɪə $ -waɪr/ noun [countable] PMa wire stretched across the ground as part of a trap
Examples from the Corpus
tripwire• We had triple concertina wire set up, claymores, and tripwires, and we even cut some fields of fire.• Another edges his way towards him ... picking through mines and tripwires.• That could include traditional diplomacy, peace-monitoring, the placing of tripwire forces on disputed borders and the policing of arms embargoes.• At first they were detonated by cables or tripwires.• Booby traps were usually small and frequently made out of a grenade, with a simple tripwire attached. 