'Vigilant' definitions:

Definition of 'vigilant'

From: WordNet
adjective
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" [syn: argus-eyed, open-eyed, vigilant, wakeful]

Definition of 'Vigilant'

From: 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]

Synonyms of 'vigilant'

From: Moby Thesaurus