noun

1. A finger-operated lever used to fire a gun.

   “Just pull the trigger.”

2. A similar device used to activate any mechanism.

3. An event that initiates others, or incites a response.

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

verb

1. To fire a weapon.

2. To initiate something.

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

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

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

Synonyms: activate, detonate, fire, activate, initiate, push someone's buttons