alarm
noun
°A summons to arms, as on the approach of an enemy.
"''Arming to answer in a night alarm. --Shakespeare."
°Any sound or information intended to give notice of approaching danger; a warning sound to arouse attention; a warning of danger.
"''Sound an alarm in my holy mountain. --Joel ii. 1."
verb
°To call to arms for defense.
°To give (someone) notice of approaching danger.