Synonyms and related words :
accidental, adventitious, aleatory, arguable, at issue, capricious, casual, causeless, chance, chancy, confutable, conjectural, contestable, contingent, controversial, controvertible, debatable, deniable, destinal, dicey, disputable, doubtable, doubtful, dubious, dubitable, erratic, fatal, fatidic, fluctuant, fluky, fortuitous, in dispute, in doubt, in dubio, in question, incalculable, incidental, indeterminate, mistakable, moot, open to doubt, open to question, problematic, questionable, refutable, risky, speculative, suppositional, suspect, suspicious, uncaused, undetermined, unexpected, unforeseeable, unforeseen, unlooked-for, unpredictable, whimsical