The Collaborative International Dictionary of English v.0.48:

Deathless \Death"less\, a.
   Not subject to death, destruction, or extinction; immortal;
   undying; imperishable; as, deathless beings; deathless fame.
   [1913 Webster]

WordNet (r) 3.0 (2006):

deathless
    adj 1: never dying; "his undying fame" [syn: deathless,
           undying]

Moby Thesaurus II by Grady Ward, 1.0:

34 Moby Thesaurus words for "deathless":
   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