Synonyms and related words :
arguable, at issue, confutable, conjectural, contestable, controversial, controvertible, debatable, defeasible, deniable, disprovable, disputable, doubtable, doubtful, dubious, dubitable, iffy, in dispute, in doubt, in dubio, in question, mistakable, moot, open to doubt, open to question, problematic, questionable, speculative, suppositional, suspect, suspicious