trigger ( triggers plural & 3rd person present) ( triggering present participle) ( triggered past tense & past participle )
1 n-count The trigger of a gun is a small lever which you pull to fire it.
A man pointed a gun at them and pulled the trigger.
2 n-count The trigger of a bomb is the device which causes it to explode.
oft N n
...trigger devices for nuclear weapons.
3 verb To trigger a bomb or system means to cause it to work.
The thieves must have deliberately triggered the alarm and hidden inside the house... V n
4 verb If something triggers an event or situation, it causes it to begin to happen or exist.
...the incident which triggered the outbreak of the First World War... V n
Trigger off means the same as trigger., phrasal verb
It is still not clear what events triggered off the demonstrations. V P n (not pron), Also V n P
5 n-count If something acts as a triggerfor another thing such as an illness, event, or situation, the first thing causes the second thing to begin to happen or exist. oft N for n Stress may act as a trigger for these illnesses.
If you describe something as hair-trigger, you mean that it is likely to change very violently and suddenly. adj ADJ n
His boozing, arrogance, and hair-trigger temper have often led him into ugly nightclub brawls..., A hair-trigger situation has been created which could lead to an outbreak of war at any time.
trigger-happy , trigger happy
If you describe someone as trigger-happy, you disapprove of them because they are too ready and willing to use violence and weapons, especially guns.
Some of them are a bit trigger-happy<endash>they'll shoot at anything that moves.