vigilant (
http://definr.com/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]