(a.) Incapable of being subdued by force; impregnable; unconquerable.

abiding amaranthine embalmed eternal ever-fresh everlasting fadeless frozen immortal imperishable impregnable incorruptible indelible indestructible ineffaceable ineradicable inexpugnable inextinguishable invincible invulnerable lasting never-dying never-ending nonperishable permanent persisting quenchless timeless undampable undestroyable undying unending unfading unquenchable