alarm
n. C / Un. a loud sound that warns you about danger or wakes you up from sleep. It can also mean a sudden feeling of fear or worry that something bad is happening.
n. a warning signal, typically audible, indicating danger or the need for immediate action; also, a sudden state of anxiety or apprehension caused by the awareness of danger.
The fire alarm rings during the drill.
The security guard raised the alarm after noticing that the back door of the warehouse was unlocked.
The sudden drop in the company's stock price caused considerable alarm among the board members, who immediately called for an emergency meeting to discuss their strategy.
From Middle English alarme, alarom, borrowed from Middle French alarme, itself from Old Italian all'arme! (“to arms!, to the weapons!”), ultimately from Latin arma (“arms, weapons”).
Countable when referring to a device or a specific warning signal; uncountable when referring to the general feeling of fear or anxiety.