automobile horn, car horn, motor horn, hooter, horn - a device on an automobile for making a warning noise

burglar alarm - a warning device that is tripped off by the occurrence of a burglary

device - an instrumentality invented for a particular purpose; "the device is small enough to wear on your wrist"; "a device intended to conserve water"

smoke alarm, fire alarm - an alarm that is tripped off by fire or smoke

horn - an alarm device that makes a loud warning sound

siren - an acoustic device producing a loud often wailing sound as a signal or warning