adj. 25B6; adjective
he was trained to be wary : CAUTIOUS, careful, circumspect, on one's guard, chary, alert, on the lookout, on one's toes, on the qui vive; attentive, heedful, watchful, vigilant, observant; informal wide awake.
we are wary of strangers : SUSPICIOUS, chary, leery, careful, distrustful, mistrustful, sceptical, doubtful, dubious.
inattentive, trustful.