on guard

Synonyms and related words:

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