tripwire

plural tripwires · alternative trip wire

1. A cord or wire arranged so that when snagged or pulled by an intruder, it will trigger a detector or trap or a device, such as a land mine.

   Seeing the tripwire of a nearby bouncing Betty gave us cold chills, and we moved all the more slowly through the woods.

   2 more examples

   They watched the two ghost-hunters run own the corridor and go crashing over the trip-wire.

   1971, Richard Carpenter, Catweazle and the Magic Zodiac, Harmondsworth: Puffin Books, page 119

   Thirteen people were injured in August 1957 when this Bristol freighter skidded on the runway at Southend Airport when landing with a flight from Calais. It ploughed through the boundary fence, but thankfully stopped short of the railway and the 1,500V overhead wires. A tripwire was installed on this section of Shenfield-Southend line to warn train drivers of instances such as this.

   2020 December 30, Tim Dunn, “The railway's mechanical marvels”, in Rail, page 58, photo caption

   Synonyms: trip cord, tripline

2. figurativelyAny means of detecting intruders or attackers.

   The continued presence of U.S. troops as a tripwire force in Macedonia is an increasingly risky venture.

   1994, Diplomat, volume 5, page 67

present singular third person tripwires · participle present tripwiring · participle past tripwired · past tripwired · alternative trip wire

1. transitiveTo set a tripwire mechanism in (a location).