1. 
[syn: argus-eyed, open-eyed, vigilant, wakeful]
The Collaborative International Dictionary of English v.0.48:
Open-eyed \O"pen-eyed`\, a.
   With eyes widely open; alert to possible danger; watchful;
   vigilant. --Shak.
   Syn: argus-eyed, hawk-eyed, unsleeping, vigilant, wary,
        watchful.
        [1913 Webster + WordNet 1.5]
WordNet (r) 3.0 (2006):
open-eyed
    adj 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" [syn: argus-eyed, open-eyed, vigilant,
           wakeful]