DOUBTFUL Meaning of DOUBTFUL in English a. 1.Wavering, undecided, hesitating, undetermined, in suspense.2.Ambiguous, dubious, equivocal, obscure, enigmatical, problematical.3.Indeterminate, undecided, uncertain, questionable. Soule. Dictionary of English synonyms. Словарь английских синонимов. 2012