alarm

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun Sudden fear or concern caused by the realization of danger or an impending setback. synonym: fear.
• noun A warning of existing or approaching danger.
• noun A device that is used to warn of danger by means of a sound or signal.
• noun The sounding mechanism of an alarm clock.
• noun A call to arms.
• transitive verb To fill with alarm or anxious concern. synonym: frighten.
• transitive verb To give warning to.
• transitive verb To equip with or protect by an alarm.

from The Century Dictionary.

• noun A summons to arms, as on the approach of an enemy; hence, any sound, outcry, or information intended to give notice of approaching danger.
• noun A hostile attack; a tumult; a broil; a disturbance.
• noun A sudden fear or painful suspense excited by an apprehension of danger; apprehension; fright: as, there is nothing in his illness to cause alarm.
• noun A warning sound; a signal for attention; an urgent call, summons, or notification.
• noun A self-acting contrivance of any kind used to call attention, rouse from sleep, warn of danger, etc.
• noun Alarm, Apprehension, Fright, Terror, Dismay, Consternation, Panic, affright, agitation, flutter, perturbation. These words all express degrees of fear in view of possible or certain, perhaps imminent, danger.
• noun Apprehension is the lowest degree of fear; the mind takes hold of the idea of danger, and without alarm considers the best way of meeting it.
• noun Alarm is the next stage; by derivation it is the alarum or summons to arms. The feelings are agitated in view of sudden or just-discovered danger to one's self or others. Generally its effect upon the mind is like that of apprehension; it energizes rather than overpowers the mental faculties.
• noun Fright, terror, and dismay are higher and perhaps equal degrees of fear; their difference is in kind and in effect.
• noun Fright affects especially the nerves and senses, being generally the effect of sudden fear.
• noun Terror may be a later form of fright, or independent and as sudden; it overpowers the understanding and unmans one.
• noun Dismay appals or breaks down the courage and hope, and therefore, as suggested by its derivation, the disposition to do anything to ward off the peril; what dismays one may be the failure or loss of his chosen means of defense.
• noun Fright and terror are often the effect of undefined fears, as in superstition, and are especially used with reference to physical fear.
• noun Consternation overwhelms the mental faculties by the suddenness or the utterly unexpected greatness of the danger.
• noun Panic is a peculiar form of fear; it is sudden, demoralizing, a temporary madness of fear, altogether out of proportion to its cause; there may even be no cause discoverable. It is the fear of a mass of people, or, figuratively, of animals.
• To call to arms for defense; give notice of danger to; rouse to vigilance and exertions for safety: as, alarm the watch.
• To surprise with apprehension of danger; disturb with sudden fear; fill with anxiety by the prospect of evil.
• To give an alarm.

from the GNU version of the Collaborative International Dictionary of English.

• noun A summons to arms, as on the approach of an enemy.
• noun Any sound or information intended to give notice of approaching danger; a warning sound to arouse attention; a warning of danger.
• noun rare A sudden attack; disturbance; broil.
• noun Sudden surprise with fear or terror excited by apprehension of danger; in the military use, commonly, sudden apprehension of being attacked by surprise.
• noun A mechanical contrivance for awaking persons from sleep, or rousing their attention; an alarum.
• noun a bell that gives notice on danger.
• noun 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.
• noun 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.
• noun a place to which troops are to repair in case of an alarm.
• transitive verb 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.
• transitive verb To keep in excitement; to disturb.
• transitive verb To surprise with apprehension of danger; to fill with anxiety in regard to threatening evil; to excite with sudden fear.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun A summons to arms, as on the approach of an enemy.
• noun Any sound or information intended to give notice of approaching danger; a warning sound to arouse attention; a warning of danger.
• noun Sudden surprise with fear or terror excited by apprehension of danger; in the military use, commonly, sudden apprehension of being attacked by surprise.
• noun A mechanical device for awaking people, or rousing their attention.
• noun An instance of an alarum ringing or clanging, to give a noise signal at a certain time.
• verb To call to arms for defense
• verb To give (someone) notice of approaching danger
• verb To rouse to vigilance and action; to put on the alert.
• verb To surprise with apprehension of danger; to fill with anxiety in regard to threatening evil; to excite with sudden fear.
• verb To keep in excitement; to disturb.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• verb warn or arouse to a sense of danger or call to a state of preparedness