trigger

/ˈtrɪɡər/
verb
  1. To cause something to start or happen.
    • The alarm system triggers a loud siren when a window is opened.
    • His comment triggered an angry response from the crowd.
    • Eating too much sugar can trigger a spike in your energy levels.
  2. To cause a device or mechanism to operate.
    • A small lever triggers the trap door to open.
    • The motion sensor triggers the lights to turn on automatically.
    • Pressing the button triggers the camera to take a photo.
Antonyms
noun
  1. The small part of a gun that you press with your finger to fire it.
    • Always treat a gun as if the trigger could be pulled at any moment.
    • The soldier slowly squeezed the trigger to fire the rifle.
    • He kept his finger off the trigger until he was ready to shoot.
  2. Something that causes a reaction or event to happen.
    • The loud noise was the trigger for the dog's barking.
    • Certain foods can act as a trigger for allergies.
    • Stress can be a trigger for headaches.