on the alert

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1. Vigilantly attentive; watchful: alert to danger; an alert bank guard. See Synonyms at careful.
2. Mentally responsive and perceptive; quick.
3. Brisk or lively in action: the bird's alert hopping from branch to branch.
1. A signal that warns of attack or danger: Sirens sounded the alert for an air raid.
2. A condition or period of heightened watchfulness or preparation for action: Nuclear-armed bombers were put on alert during the crisis.
tr.v. a·lert·ed, a·lert·ing, a·lerts
To notify of approaching danger or action; warn: a flashing red light that alerted motorists to trouble ahead.
on the alert
Watchful and prepared for danger, emergency, or opportunity: bird watchers on the alert for a rare species.

[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).]

a·lert′ly adv.
a·lert′ness n.
مُتَأهِّب، فِي حَالَة تَأهُّب
ve střehu
éberen õrködik
á varîbergi


(əˈləːt) adjective
1. quick-thinking. She's very old but still very alert.
2. (with to) watchful and aware. You must be alert to danger.
a signal to be ready for action.
to make (someone) alert; to warn. The sound of gunfire alerted us to our danger.
aˈlertly adverb
aˈlertness noun
on the alert
on the watch (for). We were on the alert for any sound that might tell us where he was.
References in classic literature ?
He did everything with an air which put your attention on the alert and raised your expectations, but the result somehow was always on stereotyped lines, unsuggestive, empty of any lesson that one could lay to heart.
In an instant I was on the alert, for there could be no wood within that buried river that had not been man brought.
I have heard them called bold and flaunting, but to me they seem modest grace itself, only always on the alert to enjoy life as much as they can and not afraid of looking the sun or anything else above them in the face.