vigilant

Adjective

WordNet 3.0

Adjective (1)

carefully observant or attentive; on the lookout for possible danger“a policy of open-eyed awareness”“the vigilant eye of the town watch”“there was a watchful dignity in the room”“a watchful parent with a toddler in tow”Synonyms: argus-eyed open-eyed wakeful

Webster's Dictionary (GCIDE)

Vigilant \Vig"i*lant\, a. [L. vigilans, -antis, p. pr. of vigilare to watch, fr. vigil awake: cf. F. vigilant. See Vigil.] Attentive to discover and avoid danger, or to provide for safety; wakeful; watchful; circumspect; wary. "Be sober, be vigilant." --1 Pet. v. 8. [1913 Webster]

Sirs, take your places, and be vigilant. --Shak. [1913 Webster]