trip wire

Noun trip wire has 2 senses

• trip wire(n = noun.group) - a small military force that serves as a first line of defense; if they become engaged in hostilities it will trigger the intervention of stronger military forces;
is a kind of force, military force, military group, military unit

• trip wire(n = noun.artifact) - a wire stretched close to the ground that activates something (a trap or camera or weapon) when tripped over;
is a kind of wire