Webster's Revised Unabridged Dictionary · 1913

Alarm

Alarm (ȧ*larm") , noun

[French alarme, Italian all' arme to arms! from Latin arma, pl., arms. See Arms, and compare Alarum.]

1.
A summons to arms, as on the approach of an enemy.
Arming to answer in a night alarm. — Shakespeare
2.
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
3.
A sudden attack; disturbance; broil. [Rare]
These home alarms. — Shakespeare
Thy palace fill with insults and alarms. — Pope
4.
Sudden surprise with fear or terror excited by apprehension of danger; in the military use, commonly, sudden apprehension of being attacked by surprise.
Alarm and resentment spread throughout the camp. — Macaulay
5.
A mechanical contrivance for awaking persons from sleep, or rousing their attention; an alarum.
Collocations (4)
Alarm bell , a bell that gives notice on danger.
Alarm clock or watch , a clock or watch which can be so set as to ring or strike loudly at a prearranged hour, to wake from sleep, or excite attention.
Alarm gauge , a contrivance attached to a steam boiler for showing when the pressure of steam is too high, or the water in the boiler too low.
Alarm post , a place to which troops are to repair in case of an alarm.

Alarm ({not transcribed}) , transitive verb

[Alarm, n. Compare French alarmer.]

1.
To call to arms for defense; to give notice to (any one) of approaching danger; to rouse to vigilance and action; to put on the alert.
2.
To keep in excitement; to disturb.
3.
To surprise with apprehension of danger; to fill with anxiety in regard to threatening evil; to excite with sudden fear.
Alarmed by rumors of military preparation. — Macaulay