The Collaborative International Dictionary of English v.0.48:

Confutative \Con*fut"a*tive\, a.
   Adapted or designed to confute. --Bp. Warburton
   [1913 Webster]

WordNet (r) 3.0 (2006):

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