siren
n. countablen. a device that makes a very loud, high sound to warn people of danger. You usually hear them on police cars, ambulances, or fire trucks.
n. an acoustic device that produces a loud, piercing sound as a warning signal. Often mounted on emergency vehicles or used for public safety alerts.
The ambulance turned on its siren to get through traffic.
The city tests the air-raid siren every first Monday of the month to ensure the public remains prepared.
As the storm approached the coastline, the distant wail of a siren signaled that residents should seek immediate shelter in the designated underground bunkers.
The name was intended to be Syren, from Swedish syren (“lilac”), but this was "corrected" by the US Post Office to Siren, who thought the name applied for was a misspelling.
Often used with verbs like 'sound', 'wail', or 'go off'.