The Collaborative International Dictionary of English v.0.48:

Refutable \Re*fut"a*ble\ (r?*f?t"?*b'l;277), a. [Cf. F.
   r['e]futable.]
   Admitting of being refuted or disproved; capable of being
   proved false or erroneous.
   [1913 Webster]

WordNet (r) 3.0 (2006):

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

Moby Thesaurus II by Grady Ward, 1.0:

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



The Free On-line Dictionary of Computing (30 December 2018):

refutable

    In lazy functional languages, a refutable pattern
   is one which may fail to match.  An expression being matched
   against a refutable pattern is first evaluated to head normal
   form (which may fail to terminate) and then the top-level
   constructor of the result is compared with that of the pattern.
   If they are the same then any arguments are matched against the
   pattern's arguments otherwise the match fails.

   An irrefutable pattern is one which always matches.  An attempt to
   evaluate any variable in the pattern forces the pattern to be
   matched as though it were refutable which may fail to match
   (resulting in an error) or fail to terminate.

   Patterns in Haskell are normally refutable but may be made
   irrefutable by prefixing them with a tilde (~).  For example,

   	(\ (x,y) -> 1) undefined	==>	undefined
   	(\ ~(x,y) -> 1) undefined	==>	1

   Patterns in Miranda are refutable, except for tuples which are
   irrefutable.  Thus

   	g [x] = 2
   	g undefined			==>	undefined

   	f (x,y) = 1
   	f undefined			==>	1

   Pattern bindings in local definitions are irrefutable in both
   languages:

   	h = 1 where [x] = undefined	==>	1

   Irrefutable patterns can be used to simulate unlifted products
   because they effectively ignore the top-level constructor of the
   expression being matched and consider only its components.

   (2013-11-03)