indefeasible (adj.)
- certain
- changeless
- constant
- fated
- fateful
- immutable
- inalienable
- incommutable
- inconvertible
- ineluctable
- inert
- inescapable
- inevitable
- inexorable
- inflexible
- invariable
- irresistible
- irretrievable
- irreversible
- irrevocable
- lasting
- necessary
- noble
- noncommunicable
- noncontagious
- noninfectious
- nonreturnable
- nonreversible
- permanent
- relentless
- resistless
- sure
- unalterable
- unaltered
- unavoidable
- unchangeable
- unchanged
- unchanging
- uncontrollable
- undeviating
- unmodifiable
- unpreventable
- unremitting
- unstoppable
- unsusceptible
- unvarying
- unyielding
