Source : Webster's Revised Unabridged Dictionary (1913)

Indeterminable \In`de*ter"mi*na*ble\, a. [L. indeterminabilis:
   cf. F. ind['e]terminable. See {In-} not, and Determine.]
   Not determinable; impossible to be determined; not to be
   definitely known, ascertained, defined, or limited. --
   {In`de*ter"mi*na*bly}, adv.

Indeterminable \In`de*ter"mi*na*ble\, n.
   An indeterminable thing or quantity. --Sir T. Browne.

Source : WordNet®

indeterminable
     adj 1: not capable of being definitely decided or ascertained [syn:
             {undeterminable}] [ant: {determinable}]
     2: unable to be determined