An instrument or device used to sound an alarm or signal a warning, such as a siren.

An alarm or siren sounded to warn the public of an approaching aerial attack by enemy aircraft

To run for shelter or seek safety upon hearing an air raid siren

A signal or warning issued when enemy aircraft approach or enter national airspace; an air-raid alarm

a warning or alert issued for a typhoon occurring at sea

To sound a siren or warning signal to alert people of an imminent or potential danger