1. (a.) Incapable of being turned back; irrevocable\; incapable of being made to run backward; as, an irreversible engine.

2. (a.) Incapable of being reversed, recalled, repealed, or annulled; as, an irreversible sentence or decree.

beyond recall beyond remedy changeless chronic confirmed constant cureless deep-dyed deep-fixed deep-rooted deep-seated deep-set deep-settled direct dyed-in-the-wool established fast final fixed gone immediate immedicable immutable implanted incommutable inconvertible incorrigible inculcated incurable indefeasible inert infixed ingrained inoperable instilled insusceptible of change intransmutable invariable inveterate irreclaimable irrecoverable irredeemable irreformable irremediable irreparable irretrievable irrevocable lasting long-established lost noble nonreturnable nonreversible one-way past hope past praying for permanent remediless reverseless rooted ruined set settled settled in habit straight straightaway straightforward straightway terminal thorough unalterable unalterative unaltered unbroken unchangeable unchanged unchanging undeflectable undeviating undone unidirectional uninterrupted unmitigable unmodifiable unrelievable unremitting unrestorable unreturnable unsalvable unsalvageable unsusceptible unswerving unvariable unvarying