The Collaborative International Dictionary of English v.0.48:

Eternity \E*ter"ni*ty\, n.; pl. Eternities. [F.
   ['e]ternit['e], L. aeternitas, fr. aeternus. See Etern.]
   1. Infinite duration, without beginning in the past or end in
      the future; also, duration without end in the future;
      endless time.
      [1913 Webster]

            The high and lofty One, that inhabiteth eternity.
                                                  --Is. lvii.
                                                  15.
      [1913 Webster]

   2. Condition which begins at death; immortality.
      [1913 Webster]

            Thou know'st 't is common; all that lives must die,
            Passing through nature to eternity.   --Shak.
      [1913 Webster]

WordNet (r) 3.0 (2006):

eternity
    n 1: time without end [syn: eternity, infinity]
    2: a state of eternal existence believed in some religions to
       characterize the afterlife [syn: eternity, timelessness,
       timeless existence]
    3: a seemingly endless time interval (waiting)