doubt·ful 
/ˈdaʊtfəl/ adjective
/ˈdaʊtfəl/ adjective [more doubtful; most doubtful] 1 : uncertain or unsure about something
▪ I tried to reassure them, but they remained doubtful. ▪ She gave him a doubtful look. [=a look that shows doubt] — often + about or of ▪ They were doubtful about the benefits of the new system. = They were doubtful of its benefits. 2 : not likely to be true : not probable
▪ He made the doubtful [=dubious] claim that he had never been sick a day in his life. ▪ The truth of the statements was doubtful. — often + that, if, or whether ▪ It's highly doubtful [=unlikely, improbable] that anyone will notice. ▪ It is doubtful if she really meant what she said. ▪ The situation is bad and it's doubtful whether it will get better soon. 3 : likely to be bad : not worthy of trust
▪ The water available in the village is of doubtful [=questionable] quality. ▪ Their decisions were based on data of doubtful accuracy. 4 : not certain : unknown or undecided
▪ The outcome of the election remains doubtful. ▪ The company is facing a doubtful future.
▪ I tried to reassure them, but they remained doubtful. ▪ She gave him a doubtful look. [=a look that shows doubt] — often + about or of ▪ They were doubtful about the benefits of the new system. = They were doubtful of its benefits.
▪ He made the doubtful [=dubious] claim that he had never been sick a day in his life. ▪ The truth of the statements was doubtful. — often + that, if, or whether ▪ It's highly doubtful [=unlikely, improbable] that anyone will notice. ▪ It is doubtful if she really meant what she said. ▪ The situation is bad and it's doubtful whether it will get better soon.
▪ The water available in the village is of doubtful [=questionable] quality. ▪ Their decisions were based on data of doubtful accuracy.
▪ The outcome of the election remains doubtful. ▪ The company is facing a doubtful future.
— doubt·ful·ly adverb
▪ She looked at him doubtfully.
▪ She looked at him doubtfully.
