Doubtful and For certain

Doubtful adjective - Not feeling sure about the truth, wisdom, or trustworthiness of someone or something.

For certain is an antonym for doubtful.

Nearby Words: doubt, doubtless, doubting, doubtfulness, doubted

For certain adverb - Definitely or positively (`sure' is sometimes used informally for `surely').

Doubtful is an antonym for for certain in topics: certain, definite.