Definition of: alert

(ə·lûrt′) adjective
1. Keenly watchful; on the look-out; ready for sudden action; vigilant.
2. Lively; nimble.
—noun 1 A warning against sudden attack; especially, a signal to prepare for an air raid or gas attack.
2. An alert attitude; guard; the period of preparedness for defense.
3. Aeron. The condition of an airplane which is manned and equipped to make a sortie.
—on the alert On the look-out; ready.
—v. t. To prepare for action; warn, as of a threatened attack or raid. [<F alerte <Ital. all’erta on the watch]
—a·lert′ly adverb
—a·lert′·ness noun Synonyms (adjective): active, alive, brisk, bustling, nimble, prepared, prompt, ready, vigilant, watchful, wide-awake. Alert, ready, and wide-awake refer to a watchful promptness for action. Ready suggests preparation; the wandering Indian is alert, the trained soldier is ready. Ready expresses more life and vigor than prepared. The gun is prepared; the man is ready. Prompt expresses readiness for appointment or demand at the required moment. The good general is ready for emergencies, alert to perceive opportunity or peril, prompt to seize occasion. Compare ACTIVE, ALIVE, NIMBLE. Antonyms: drowsy, dull, heavy, inactive, slow, sluggish, stupid.