WordWeb Online

1. 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"
    
2. Openly distrustful and unwilling to confide
   "He was wary of how the difficult situation would work out";
   - leery, mistrustful, suspicious, untrusting

Derived forms: warier, wariest

See also: cageyness, caginess, chariness, distrustful, on guard, on one's guard, on your guard, shy, upon one's guard, wariness

Antonym: unwary