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Meaning of tripwire

trip•wire

Pronunciation: (trip'wīr"), [key]
— n.
  1. a wire used to set off concealed explosives, as one stretched across a footpath to be struck and activated by the foot of an enemy soldier.
  2. a wire that activates a trap, camera, or other device when stepped on, tripped on, or otherwise disturbed.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.