Definition from Wiktionary, the free dictionary
trigger (plural triggers)
- A finger-operated lever used to fire a gun.
- Just pull the trigger.
- A similar device used to activate any mechanism.
- An event that initiates others, or incites a response.
- (psychology) An event, experience or other stimulus that initiates a traumatic memory or action in a person.
- (electronics) A pulse in an electronic circuit that initiates some component.
- (computing) An SQL procedure that may be initiated when a record is inserted, updated or deleted; typically used to maintain referential integrity.
- (online gaming) A text string that, when received by a player, will cause the player to execute a certain command.
- (archaic) A catch to hold the wheel of a carriage on a declivity.
Derived terms 
finger-operated lever used to fire a gun
similar device used to activate any mechanism
event that initiates others, or incites a response
- The translations below need to be checked and inserted above into the appropriate translation tables, removing any numbers. Numbers do not necessarily match those in definitions. See instructions at Help:How to check translations.
Translations to be checked
to fire a weapon
to initiate something