'Immutability' definitions:

Definition of 'immutability'

From: WordNet
noun
The quality of being incapable of mutation; "Darwin challenged the fixity of species" [syn: immutability, immutableness, fixity] [ant: mutability, mutableness]

Definition of 'Immutability'

From: GCIDE
  • Immutability \Im*mu`ta*bil"i*ty\, n. [L. immutabilitas: cf. F. immutabilit['e].] The state or quality of being immutable; immutableness. --Heb. vi. 17. [1913 Webster]