The Collaborative International Dictionary of English v.0.48:

Disputable \Dis`pu*ta*ble\ (?; 277), a. [L. disputabilis: cf. F.
   disputable. See Dispute, v. i.]
   1. Capable of being disputed; liable to be called in
      question, controverted, or contested; or doubtful
      certainty or propriety; controvertible; as, disputable
      opinions, propositions, points, or questions.
      [1913 Webster]

            Actions, every one of which is very disputable.
                                                  --Jer. Taylor.
      [1913 Webster]

   2. Disputatious; contentious. [Obs.] --Shak.
      [1913 Webster]

WordNet (r) 3.0 (2006):

disputable
    adj 1: capable of being disproved [syn: debatable,
           disputable]
    2: open to argument or debate; "that is a moot question" [syn:
       arguable, debatable, disputable, moot]

Moby Thesaurus II by Grady Ward, 1.0:

32 Moby Thesaurus words for "disputable":
   arguable, at issue, confutable, conjectural, contestable,
   controversial, controvertible, debatable, deniable, doubtable,
   doubtful, dubious, dubitable, iffy, in dispute, in doubt, in dubio,
   in question, mistakable, moot, open to doubt, open to question,
   problematic, questionable, refutable, speculative, suppositional,
   suspect, suspicious, uncertain, undecided, unsettled