The Collaborative International Dictionary of English v.0.48:

Immortality \Im`mor*tal"i*ty\, n.; pl. Immortalities. [L.
   immortalitas: cf. F. immortalit['e].]
   1. The quality or state of being immortal; exemption from
      death and annihilation; unending existance; as, the
      immortality of the soul.
      [1913 Webster]

            This mortal must put on immortality.  --1 Cor. xv.
                                                  53.
      [1913 Webster]

   2. Exemption from oblivion; perpetuity; as, the immortality
      of fame.
      [1913 Webster]

WordNet (r) 3.0 (2006):

immortality
    n 1: the quality or state of being immortal [ant: mortality]
    2: perpetual life after death

The Devil's Dictionary (1881-1906):

IMMORTALITY, n.

    A toy which people cry for,
    And on their knees apply for,
    Dispute, contend and lie for,
        And if allowed
        Would be right proud
    Eternally to die for.
                                                                  G.J.