inextinguishable (adj.)

• deathless
• enduring
• eternal
• everlasting
• immortal
• imperishable
• impregnable
• incorruptible
• indelible
• indestructible
• ineradicable
• inexpugnable
• invincible
• invulnerable
• irrepressible
• quenchless
• undestroyable
• undying
• unquenchable