adj. 1 feeling doubt or misgivings; unsure or guarded in one's opinion. 2 causing doubt; ambiguous; uncertain in meaning etc. 3 unreliable (a doubtful ally). doubtfully adv. doubtfulness n.
DOUBTFUL
Meaning of DOUBTFUL in English
Concise Oxford English dictionary. Краткий оксфордский словарь английского языка. 2012