from The American Heritage® Dictionary of the English Language, 4th Edition
- adj. Vigilantly attentive; watchful: alert to danger; an alert bank guard. See Synonyms at aware.
- adj. Mentally responsive and perceptive; quick.
- adj. Brisk or lively in action: the bird's alert hopping from branch to branch.
- n. A signal that warns of attack or danger: Sirens sounded the alert for an air raid.
- n. A condition or period of heightened watchfulness or preparation for action: Nuclear-armed bombers were put on alert during the crisis.
- transitive v. To notify of approaching danger or action; warn: a flashing red light that alerted motorists to trouble ahead.
- idiom on the alert Watchful and prepared for danger, emergency, or opportunity: bird watchers on the alert for a rare species.
from Wiktionary, Creative Commons Attribution/Share-Alike License
- adj. Attentive; awake; on-guard.
- n. An alarm.
- n. A notification of higher importance than an advisory.
- v. To give warning to.
from the GNU version of the Collaborative International Dictionary of English
- adj. Watchful; vigilant; active in vigilance.
- adj. Brisk; nimble; moving with celerity.
- n. An alarm from a real or threatened attack; a sudden attack; also, a bugle sound to give warning.
from The Century Dictionary and Cyclopedia
- Active in vigilance; watchful; vigilantly attentive.
- Moving with celerity; brisk; active; nimble: as, “an alert young fellow,” Addison, Spectator, No. 403.
- Lively, agile, quick, prompt, ready, spry.
- n. An attitude of vigilance; watch; guard: especially in the phrase on or upon the alert, upon the watch; on the lookout; guarding against surprise or danger: as, “the readiness of one on the alert,” Dickens.
from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
- adj. engaged in or accustomed to close observation
- adj. mentally perceptive and responsive
- v. warn or arouse to a sense of danger or call to a state of preparedness
- adj. quick and energetic
- n. a warning serves to make you more alert to danger
- n. condition of heightened watchfulness or preparation for action
- n. an automatic signal (usually a sound) warning of danger
French alerte, from Italian all' erta, on the lookout : alla, to the, on the (from Latin ad illam, to that : ad, to; see ad- + illam, feminine accusative sing. of ille, that, the.(American Heritage® Dictionary of the English Language, Fourth Edition)
From French alerte ("alert"), from the phrase à l'erte ("on the watch"), from Italian all'erta ("to the height"), from erta ("lookout, tower"). (Wiktionary)