tripwire

trip +‎ wire

tripwire (plural tripwires)

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.

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

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

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

     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.

2. Any means of detecting intruders or attackers.
   • 1994, Diplomat, volume 5, page 67:

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

• trip wire

• tripline
• trip cord

• land mine
• explosive

tripwire (third-person singular simple present tripwires, present participle tripwiring, simple past and past participle tripwired)

1. (transitive) To set a tripwire mechanism in (a location).