godan verb (-ru), transitive verb
doubt; distrust; be suspicious of; suspect
Colloquial verb for doubting someone's words, motives, or trustworthiness. Stronger than 疑う (うたがう) and often implies a personal, emotional distrust.
彼の言うことを疑る。
I doubt what he says.
あの人はすぐ人を疑るから、友達が少ない。
That person is quick to distrust others, so they have few friends.