A benign situation initially mistaken for an emergency. Mary thought she was going into labor, but it turned out to be a false alarm.When the smoke detectors started beeping, we thought the building was on fire, but it was just a false alarm caused by faulty wiring.
A warning signal that is groundless, made either by mistake or as a deliberate deception. For example, The rumor that we were all going to get fired was just a false alarm, or Setting off a false alarm is a criminal offense. This expression, first recorded in 1579, today is often used for a report of a nonexistent fire.