Source : Webster's Revised Unabridged Dictionary (1913)

Illimitable \Il*lim"it*a*ble\, a. [Pref. il- not + limitable:
   cf. F. illimitable.]
   Incapable of being limited or bounded; immeasurable;
   limitless; boundless; as, illimitable space.

         The wild, the irregular, the illimitable, and the
         luxuriant, have their appropriate force of beauty. --De
                                                  Quincey.

   Syn: Boundless; limitless; unlimited; unbounded;
        immeasurable; infinite; immense; vast. --
        {Il*lim"it*a*ble*ness}, n. -- {Il*lim"it*a*bly}, adv.

Source : WordNet®

illimitable
     adj : without limits in extent or size or quantity; "immeasurable
           vastness of our solar system" [syn: {limitless}, {measureless},
            {unmeasured}]