The definition of a hair trigger is a gun trigger that goes off with a very light squeeze.
An example of a hair trigger is a pistol that's been adjusted so it goes off very easily.
Hair trigger defines something that responds or happens easily or without cause.
An example of hair trigger is a person who gets angry instantly; a hair trigger temper.
A gun trigger adjusted to respond to a very slight pressure.
Responding to the slightest provocation or stimulation.
A hair-trigger temper; a hair-trigger reaction.
A trigger so delicately adjusted that a very slight pressure on it discharges the firearm.
Set in motion or operation by a very slight impulse.