trigger
noun [ C, usually singular ]
uk/ˈtrɪɡər/ usan event, situation, etc. that causes the start of something, especially something bad:
trigger for sth Inflation has been the trigger for nearly all post-war recessions.
trigger
verb [ T ]
uk/ˈtrɪɡər/ usto cause something to happen, especially something bad:
Central banks must raise interest rates without triggering a financial crisis for households with excessive debts.
be triggered by sth The sell-off was triggered by a profits warning.
to make a piece of equipment, etc. start working:
Any attempt to jack the car off the ground triggers the alarm automatically.