The term ALARM TRIGGER can be summarized as a device that sets off an alarm when activated. In this case, the crossword solution for ALARM TRIGGER is SMOKE, which indicates that SMOKE detectors are a common type of alarm trigger. SMOKE detectors detect SMOKE particles in the air and set off an alarm when they detect a certain level of SMOKE. This is an important safety feature in many homes and businesses, as it can alert people to the presence of a fire before it spreads.