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

  • adjective Vigilantly attentive; watchful: synonym: careful.
  • adjective Mentally responsive and perceptive; quick.
  • adjective Brisk or lively in action.
  • noun A signal that warns of attack or danger.
  • noun A condition or period of heightened watchfulness or preparation for action.
  • transitive verb To notify of approaching danger or action; warn.
  • idiom (on the alert) Watchful and prepared for danger, emergency, or opportunity.

from The Century Dictionary.

  • 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.
  • noun 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 the GNU version of the Collaborative International Dictionary of English.

  • adjective Watchful; vigilant; active in vigilance.
  • adjective Brisk; nimble; moving with celerity.
  • noun (Mil.) An alarm from a real or threatened attack; a sudden attack; also, a bugle sound to give warning.
  • noun on the lookout or watch against attack or danger; ready to act.

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

  • adjective Attentive; awake; on-guard.
  • noun An alarm.
  • noun A notification of higher importance than an advisory.
  • verb To give warning to.

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

  • adjective engaged in or accustomed to close observation
  • adjective mentally perceptive and responsive
  • verb warn or arouse to a sense of danger or call to a state of preparedness
  • adjective quick and energetic
  • noun a warning serves to make you more alert to danger
  • noun condition of heightened watchfulness or preparation for action
  • noun an automatic signal (usually a sound) warning of danger


from The American Heritage® Dictionary of the English Language, 4th Edition

[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; see al- in Indo-European roots) + erta, lookout (from past participle of ergere, to raise, from Latin ērigere; see erect).]

from Wiktionary, Creative Commons Attribution/Share-Alike License

From French alerte ("alert"), from the phrase à l'erte ("on the watch"), from Italian all'erta ("to the height"), from erta ("lookout, tower").


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  • "Communities in Healesville, Chum Creek, Badger Creek, Steels Creek, Dixons Creek, Yarra Glen, Toolangi and Castello are being advised to remain alert to fire activity."

    - CFA urges vigilance despite 'calming' threat,, 11 Feb 2009.

    Correction: although this quote says Castello, the hamlet's name is Castella. I learned this in high school when I was stopping people in the street to do a survey of their shopping habits.

    February 12, 2009

  • Be alert. The world needs more lerts.

    March 25, 2009

  • Should I also be amoral because the world needs more morals?

    March 25, 2009