The Collaborative International Dictionary of English v.0.48:

Debatable \De*bat"a*ble\, a. [Cf. OF. debatable. See Debate.]
   Liable to be debated; disputable; subject to controversy or
   contention; open to question or dispute; as, a debatable
   question.
   [1913 Webster]

   The Debatable Land or or Ground, a tract of land between
      the Esk and the Sark, claimed by both England and
      Scotland; the Batable Ground.
      [1913 Webster]