vigilant
1. [ adjective ] carefully observant or attentive; on the lookout for possible danger
Synonyms: wakeful watchful open-eyed argus-eyed
Examples:

"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"

Related terms: alert
2. [ adjective ] carefully observant or attentive; on the lookout for possible danger
Synonyms: wakeful watchful open-eyed argus-eyed
Examples:

"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"

Related terms: alert
Similar spelling:   vigilante
  vigilantly
  vigilantism
  vigilance