Pronunciation: (trig'ur),[key] —n. 1. a small projecting tongue in a firearm that, when pressed by the finger, actuates the mechanism that discharges the weapon.
2. a device, as a lever, the pulling or pressing of which releases a detent or spring.
3. anything, as an act or event, that serves as a stimulus and initiates or precipitates a reaction or series of reactions.
5. quick on the trigger,Informal.quick to act or respond; impetuous; alert.
—v.t. 1. to initiate or precipitate (a chain of events, scientific reaction, psychological process, etc.): Their small protest triggered a mass demonstration. 2. to fire or explode (a gun, missile, etc.) by pulling a trigger or releasing a triggering device: He accidentally triggered his rifle.
—v.i. 1. to release a trigger.
2. to become active; activate.