The Collaborative International Dictionary of English v.0.48:

Confutable \Con*fut"a*ble\, a.
   That may be confuted.
   [1913 Webster]

         A conceit . . . confutable by daily experience. --Sir
                                                  T.Browne.
   [1913 Webster]

WordNet (r) 3.0 (2006):

confutable
    adj 1: able to be refuted [syn: questionable, refutable,
           confutable, confutative]