1) Ageless 2) Binding 3) Changeless 4) Unchallengeable 5) Unmutable 1) Changeless 2) French word used in English 3) Not mutable 4) That cannot be changed 5) Unchangeable 
• (a.) Not mutable; not capable or susceptible of change; unchangeable; unalterable.
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) ... Origin: L. Immutabilis; pref. Im- not + mutabilis mutable. See Mutable. ... Source: Web...
Im·mu'ta·ble adjective [ Latin immutabilis ; prefix 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 h...
that cannot be changed 
Cannot be changed after its created.
[adj] - not subject or susceptible to change or variation in form or quality or nature
An object with fixed value. Immutable objects include numbers, strings and tuples. Such an object cannot be altered. A new object has to be created if a different value has to be stored. They play an important role in places where a constant hash value is needed such as the keys of a dictionary.
adjective not subject or susceptible to change or variation in form or quality or nature; `the view of that time was that all species were immutable, created by God`
not mutable; unchangeable; changeless.
[PSAT glossary] not subject or susceptible to change or variation not subject or susceptible to change or variation[Intelligent words] not subject or susceptible to change or variation