dubious

"they were doubtful that the cord would hold"; "it was doubtful whether she would be admitted"; "dubious about agreeing to go";

"the candidate's doubtful past"; "he has a dubious record indeed"; "what one found uncertain the other found dubious or downright false"; "it was more than dubitable whether the friend was as influential as she thought";

"they admitted the force of my argument but remained dubious";