The Collaborative International Dictionary of English v.0.48:
Alarm \A*larm"\ ([.a]*l[aum]rm"), n. [F. alarme, It. all' arme
to arms ! fr. L. arma, pl., arms. See Arms, and cf.
1. A summons to arms, as on the approach of an enemy.
Arming to answer in a night alarm. --Shak.
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. [R.] "These home
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.
5. A mechanical contrivance for awaking persons from sleep,
or rousing their attention; an alarum.
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.
Syn: Fright; affright; terror; trepidation; apprehension;
consternation; dismay; agitation; disquiet; disquietude.
Usage: Alarm, Fright, Terror, Consternation. These
words express different degrees of fear at the
approach of danger. Fright is fear suddenly excited,
producing confusion of the senses, and hence it is
unreflecting. Alarm is the hurried agitation of
feeling which springs from a sense of immediate and
extreme exposure. Terror is agitating and excessive
fear, which usually benumbs the faculties.
Consternation is overwhelming fear, and carries a
notion of powerlessness and amazement. Alarm agitates
the feelings; terror disorders the understanding and
affects the will; fright seizes on and confuses the
sense; consternation takes possession of the soul, and
subdues its faculties. See Apprehension.