unsupportable

from WordNet (r) 3.0 (2006)

unsupportable
    adj 1: not able to be supported or defended

from The Collaborative International Dictionary of English v.0.48

Unsupportable \Un`sup*port"a*ble\, a.
   Insupportable; unendurable. -- {Un`sup*port"a*ble*ness}, n.
   --Bp. Wilkins. -- {Un`sup*port"a*bly}, adv.
   [1913 Webster]

from Moby Thesaurus II by Grady Ward, 1.0

28 Moby Thesaurus words for "unsupportable":
      baseless, controvertible, empty, groundless, idle, ill-founded,
      insupportable, intolerable, unattestable, unbased, unbearable,
      unconfirmable, undemonstrable, undemonstratable, unendurable,
      unfounded, ungrounded, unprovable, unsubstantiatable, unsupported,
      unsustainable, unsustained, untenable, unverifiable, unwarranted,
      vain, without basis, without foundation