| 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. |
| 4. | Slang. triggerman. |
| 5. | to initiate or precipitate (a chain of events, scientific reaction, psychological process, etc.): Their small protest triggered a mass demonstration. |
| 6. | to fire or explode (a gun, missile, etc.) by pulling a trigger or releasing a triggering device: He accidentally triggered his rifle. |
| 7. | to release a trigger. |
| 8. | to become active; activate. |
| 9. | quick on the trigger, Informal. quick to act or respond; impetuous; alert. |