Meaning of “alarm” - Learner’s Dictionary

alarm

noun uk us /əˈlɑːm/
WARNING [ C ]

B1 a loud noise that warns you of danger:

a fire alarm
to set off an alarm
CLOCK [ C ] (also alarm clock)

B1 a clock that makes a noise to wake you

WORRY [ U ]

a sudden feeling of fear or worry that something bad might happen:

There's no need for alarm - it is completely safe.

(Definition of “alarm noun” from the Cambridge Learner’s Dictionary © Cambridge University Press)