(adv.) On the defensive.

Argus-eyed all ears all eyes at bay aux abois aux aguets canny careful cautious circumspect custodial defensively deliberate discreet eagle-eyed gingerly guarded hawk-eyed heedful hesitant in defense in self-defense judicious keen-eyed leaving out nothing lidless mindful noncommittal observant on the defensive on the lookout on the watch open-eyed overlooking no possibility pawky politic prudent regardful safe sharp-eyed sleepless slow to act tentative thorough unadventurous uncommunicative undaring unenterprising unprecipitate vigilant wary watchful with open eyes