Someone who is vigilant gives careful attention to a particular problem or situation and concentrates on noticing any danger or trouble that there might be. He warned the public to be vigilant and report anything suspicious = alert + vigilance vigi·lance Drugs are a problem that requires constant vigilance. giving careful attention to what is happening, so that you will notice any danger or illegal activity (present participle of vigilare , from vigil; VIGIL)
Attentive to discover and avoid danger, or to provide for safety; wakeful; watchful; circumspect; wary
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"