Doubtfully
Pronunciation : Doubt"ful*ly
Part of Speech : adv.
Definition : Defn: In a doubtful manner. Nor did the goddess doubtfully declare. Dryden.
Source : Webster's Unabridged Dictionary, 1913
Merriam-Webster's Everyday Language Reference Set: Includes: The Merriam-Webster Dictionary, The Merriam-Webster Thesaurus, and The Merriam-Webster Vocabulary Builder