(a.) Incapable of being recalled or revoked; unchangeable; irreversible; unalterable; as, an irrevocable promise or decree; irrevocable fate.

absolute beyond recall beyond remedy binding certain changeless compulsory conclusive constant cureless decisive decretory dictated enduring entailed established everlasting fated fateful final fixed gone hard-and-fast immedicable immutable imperative imposed incommutable inconvertible incorrigible incurable indefeasible ineluctable inert inescapable inevasible inevitable inexorable inflexible inoperable insusceptible of change intransmutable invariable irreclaimable irrecoverable irredeemable irreformable irremediable irreparable irresistible irretrievable irreversible lasting lost mandated mandatory must necessary noble nonreturnable nonreversible obligatory past hope past praying for peremptory permanent prescript prescriptive relentless remediless required resistless reverseless ruined settled sure sure as death sure as fate terminal ultimate unalterable unalterative unaltered unavoidable unchangeable unchanged unchanging uncontrollable undeflectable undeviating undone unmitigable unmodifiable unpreventable unrelievable unremitting unrestorable unreturnable unsalvable unsalvageable unstoppable unsusceptible unvariable unvarying unyielding without appeal