keeping careful watch for possible danger or difficulties.
the burglar was spotted by vigilant neighbors
同义词：
watchfulon the lookoutobservantsharp-eyedkeen-eyedgimlet-eyedeagle-eyedhawk-eyedwith eyes like a hawkwith one's eyes openkeeping one's eyes peeled/skinnedattentivepaying attentionalerton the alerton one's toeson the qui viveawakewide awakeunsleepingon one's guardon guardconcentratingcarefulcautiouswarycharycircumspectprudentheedfulmindfulpreparedreadyinformal：beady-eyednot missing a trickon the ballkeeping a weather eye on thingsleeryrare：regardfulArgus-eyed
