mindmap root((怀疑)) doubtful is likely to impute worthlessness, unsoundness, failure, or uncertainty: still ~ about the cause of the explosion. dubious stresses suspicion, mistrust, or hesitation: ~ about the practicality of the scheme. problematic applies especially to things or situations whose existence, meaning, or realization is highly uncertain: whether the project will ever be finished is ~. questionable may imply no more than the existence of doubt but usually suggests doubt about propriety or well-grounded suspicions: a real estate agent of ~ honesty.