tripwire

set off a/the tripwire

To trigger some sort of alarm or protective measure, such as a booby trap. Watch your leg! You almost set off the trip wire! When Alan set off the trip wire, he narrowly escaped being crushed by a falling boulder.

See also: off, set, tripwire

tripwire

1. A wire that, when touched or jostled, triggers some sort of alarm or protective measure, such as a booby trap. Watch your leg! Can't you see the tripwire there? When he set off the tripwire, he narrowly escaped being crushed by a falling boulder.

2. A small group of military members whose involvement in combat precedes the involvement of a larger or stronger force. Yes, we had backup, but even so, knowing the limitations of our tripwire gave me a sick feeling.

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