Source : Webster's Revised Unabridged Dictionary (1913)

Argus-eyed \Ar"gus-eyed\, a.
   Extremely observant; watchful; sharp-sighted.

Source : WordNet®

argus-eyed
     adj 1: having very keen vision; "quick-sighted as a cat" [syn: {hawk-eyed},
             {keen-sighted}, {lynx-eyed}, {quick-sighted}, {sharp-eyed},
             {sharp-sighted}]
     2: 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: {open-eyed}, {vigilant}, {wakeful}, {watchful}]