Definition of: vigilant

(vij′ə·lənt) adjective
Characterized by vigilance; being on the alert; watchful; heedful; wary. [<MF <L vigilans, -antis, ppr. of vigilare keep awake <vigil awake]
—vig′i·lant·ly adverb
—vig′i·lant·ness noun Synonyms: active, alert, awake, careful, cautious, circumspect, heedful, mindful, sleepless, wakeful, wary, watchful, wide-awake. Vigilant implies more sustained activity and more intelligent volition than alert. One is vigilant against danger; he may be alert or watchful for good as well as against evil; he is wary in view of suspected stratagem, trickery, or treachery. A person may be wakeful because of some merely physical excitement or excitability, as through insomnia; yet he may be utterly careless and negligent in his wakefulness, the reverse of watchful; a person who is truly watchful must keep himself wakeful while on watch, in which case wakeful has something of mental quality. Watchful, from the English, and vigilant, from the Latin, are almost exact equivalents; but vigilant has a somewhat sharper definiteness and somewhat more of a suggestion of volition; one may be habitually watchful; one is vigilant of set purpose and for direct cause. See ALERT. Antonyms: careless, drowsy, dull, heedless, inattentive, incautious, inconsiderate, neglectful, negligent, oblivious, thoughtless, unwary.