argus-eyed

from WordNet (r) 3.0 (2006)

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

from The Collaborative International Dictionary of English v.0.48

Argus-eyed \Ar"gus-eyed\, a.
   Extremely observant; watchful; sharp-sighted.
   [1913 Webster]