The word "unforfeitable" refers to something that cannot be taken away, lost or surrendered. Its synonyms include irrevocable, permanent, absolute, immutable, non-negotiable, secure, guaranteed, and steadfast. Irrevocable means that something cannot be altered or revoked. Permanent means that something is intended to last indefinitely. Absolute means that something is not limited by restrictions or conditions. Immutable means that something is unchanging over time. Non-negotiable means that something cannot be changed by discussion or bargaining. Secure means that something is protected from harm or theft. Guaranteed means that something is assured without a doubt. Steadfast means that something is unwavering and consistent.