adjectives
fraught with uncertainty or doubt
"they were doubtful that the cord would hold"; "it was doubtful whether she would be admitted"; "dubious about agreeing to go"
open to doubt or suspicion
"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"- Karen Horney
not convinced
"they admitted the force of my argument but remained dubious"
is similar to
lacking conviction
"I remain unconvinced"