wary

marked by keen caution and watchful prudence; "they were wary in their movements"; "a wary glance at the black clouds"; "taught to be wary of strangers"

• on guard, on one's guard(p), upon one's guard(p), on your guard — vigilant
• shy — wary and distrustful; disposed to avoid persons or things

• wariness, chariness — the trait of being cautious and watchful