assume, cavil, conjectural, controvert, cynical, cynicism, debunk, deterrent, disbelief, disbeliever, disillusion, disillusionment, dispel, dither, doubt, dubious, dubiously, fallible, faltering, flummoxed, hesitant, hesitate, implausible, inconceivable, incredulity, incredulous, incredulously, irrational, irresolute, lapse, misgiving, mistrustfully, naysayer, oppugn, qualm, questionable, rebut, refute, sceptic, shady, skeptical, skepticism, suspicion, suspicious, tentative, uncertain, unsure, untenable, vacillate, waver, wavering