[1] : The Collaborative International Dictionary of English v.0.48

vigilant \vig"ilant\, 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
see also:
vigil 

[2] : WordNet (r) 2.0

vigilant
     adj : 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, wakeful,
            watchful
see also:
argus-eyed open-eyed wakeful watchful 

[3] : Moby Thesaurus II by Grady Ward, 1.0

89 moby thesaurus words for "vigilant":
   argus-eyed, acute, agog, alert, all ears, all eyes, all ready,
   all set, armed, armed and ready, attentive, aux aguets, avid,
   booted and spurred, briefed, careful, cautious, chary, circumspect,
   coached, cocked, covering, custodial, defensive, eager, eagle-eyed,
   equipped, familiarized, fostering, good and ready, groomed,
   guarded, guardian, guarding, hawk-eyed, immunizing, in arms,
   in battle array, in readiness, in the saddle, informed, keen,
   keen-eyed, lidless, loaded, loaded for bear, mature, mobilized,
   observant, on guard, on the alert, on the lookout, on the mark,
   on the watch, open-eyed, parental, planned, prearranged, prepared,
   prepared and ready, prepped, preventive, primed, prophylactic,
   protecting, protective, provided, prudent, psyched up, ready,
   ready for anything, ripe, safeguarding, screening, set, sharp,
   sharp-eyed, sheltering, shielding, sleepless, tutelary, unsleeping,
   up in arms, wakeful, wary, watchful, well-prepared, wide-awake,
   with open eyes

Vigilant >> V Words
Vigilant, definition of term: Vigilant
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