alert

/ə-ˈlərt/

borrowed from French alerte, going back to Middle French a l'herte "on guard, on the watch," borrowed from Italian all'erta, originally in the collocation stare all'erta "to be on the watch," literally, "to be on the height" (with erta "height, hill, steep ascent," noun derivative from feminine of erto, past participle of ergere "to raise, elevate," going back to Vulgar Latin *ērgere, by syncope from Latin ērigere)

adjective

  1. watchful and prompt to meet danger or emergency

  2. quick to perceive and act

  3. active, brisk

an alert guard

mentally alert

watchful vigilant wide-awake alert mean being on the lookout especially for danger or opportunity. watchful is the least explicit term. vigilant suggests intense, unremitting, wary watchfulness.

noun

  1. a state of careful watching and readiness especially for danger or opportunity

  2. an alarm or other signal of danger

  3. an urgent notice

on 24-hour alert

verb

  1. to call (someone) to a state of readiness : warn

  2. to make (someone) aware of something

alerted the school board of a possible teachers' strike