'Trigger' definitions:

Definition of 'trigger'

noun

Lever that activates the firing mechanism of a gun [syn: gun trigger, trigger]

noun

A device that activates or releases or causes something to happen

noun

An act that sets in motion some course of events [syn: trigger, induction, initiation]

verb

Put in motion or move to act; "trigger a reaction"; "actuate the circuits" [syn: trip, actuate, trigger, activate, set off, spark off, spark, trigger off, touch off]

verb

Release or pull the trigger on; "Trigger a gun"

From: GCIDE

Trigger \Trig"ger\, n. [For older tricker, from D. trekker, fr. trekken to draw, pull. See Trick, n.]
1. A catch to hold the wheel of a carriage on a declivity. [1913 Webster]
2. (Mech.) A piece, as a lever, which is connected with a catch or detent as a means of releasing it; especially (Firearms), the part of a lock which is moved by the finger to release the cock and discharge the piece. [1913 Webster]
Trigger fish (Zool.), a large plectognath fish ({Balistes Carolinensis} or Balistes capriscus) common on the southern coast of the United States, and valued as a food fish in some localities. Its rough skin is used for scouring and polishing in the place of sandpaper. Called also leather jacket, and turbot. [1913 Webster]