Irrevocable

a. [Prefix in, not, and revocable; Fr. irrévocable, Sp. irrevocable, It. irrevocabile, Lat. irrevocabilis.] Incapable of being recalled or revoked; as, an irrevocable decree; irrevocable fate; an irrevocable promise.

Firm and irrevocable is my doom. Shak.