What does "irrevocable" mean?

Irrevocable: Incapable of being recalled or revoked; unchangeable; irreversible; unalterable; as, an irrevocable promise or decree; irrevocable fate. Firm and irrevocable is my doom. Shak. -- Ir*rev"o*ca*ble*ness, n. -- Ir*rev"o*ca*bly, adv.

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