fire alarm 
noun
A device making a loud noise that gives warning of a fire: a fire alarm went off and the building had to be evacuated...
- This time the ringing noise wasn't the fire alarm, but the dinner bell.
- That was when the idiots decided to test the fire alarm without the usual warning over the speakers.
- One girl bolted to the fire alarm and pulled it, setting the siren wailing and then sprinting for the door.
- offendent
- offender
- offender profiling
- offense
- offensive
- offensive coordinator
- offensive line
- offensive lineman
- offensively
- offensiveness
- offensive tackle
- offer
- offerable
- offer document
- offeree
- offerer
- offering
- offering price
- offer of amends
- offer one's hand
- offer price
- offertorial
- offertory
- of few words
- off-farm