trigger

firearmsA 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.

“Sleeping in an unfamiliar room can be a trigger for sleepwalking.”

A concept or image that upsets somebody by sparking a negative emotional response.

“I can't watch that violent film. Blood is one of my triggers.”

psychologyAn event, experience or other stimulus that initiates a traumatic memory or a strong reaction in a person.

musicAn electronic transducer allowing a drum, cymbal, etc. to control an electronic drum unit or similar device.

musicA device that manually lengthens (or sometimes shortens) the slide or tubing of a brass instrument, allowing the pitch range to be altered while playing.

electronicsA pulse in an electronic circuit that initiates some component.

databasesAn SQL procedure that may be initiated when a record is inserted, updated or deleted; typically used to maintain referential integrity.

online gamingA text string that, when received by a player, will cause the player to execute a certain command.

Lever that activates the firing mechanism of a gun

A device that activates or releases or causes something to happen

An act that sets in motion some course of events

To fire a weapon.

To initiate something.

“The controversial article triggered a deluge of angry letters from readers.”

figurativeTo spark a response, especially a negative emotional response, in (someone).

“This story contains a rape scene and may be triggering for rape victims.”

“* 1) (transitive, figurative, by extension of above, Internet slang) To intentionally offend someone, especially by expressing radical or edgy opinions.”

especially electronicsTo activate; to become active.

Put in motion or move to act

“trigger a reaction”

“actuate the circuits”

Release or pull the trigger on

“Trigger a gun”