Nouns

(n)misgiving, mistrust, distrust, suspiciondoubt about someone's honesty
(n)distrust, distrustfulness, mistrustthe trait of not trusting others

Verbs

(v)distrust, mistrust, suspectregard as untrustworthy; regard with suspicion; have no faith or confidence in“I suspect her true motives”, “she distrusts her stepmother”