Source : Webster's Revised Unabridged Dictionary (1913)

Immutable \Im*mu"ta*ble\, a. [L. immutabilis; pref. im- not +
   mutabilis mutable. See {Mutable}.]
   Not mutable; not capable or susceptible of change;
   unchangeable; unalterable.

         That by two immutable things, in which it was
         impossible for God to lie, we might have a strong
         consolation.                             --Heb. vi. 18.

         Immutable, immortal, infinite, Eternal King. --Milton.
   -- {Im*mu"ta*ble*ness}, n. -- {Im*mu"ta*bly}, adv.

Source : WordNet®

immutableness
     n : the quality of being incapable of mutation; "Darwin
         challenged the fixity of species" [syn: {immutability}, {fixity}]
         [ant: {mutability}, {mutability}]