Source : Webster's Revised Unabridged Dictionary (1913)

Perpetuity \Per`pe*tu"i*ty\, n. [L. perpetuitas: cf. F.
   perp['e]tuit['e].]
   1. The quality or state of being perpetual; as, the
      perpetuity of laws. --Bacon.

            A path to perpetuity of fame.         --Byron.

            The perpetuity of single emotion is insanity. --I.
                                                  Taylor.

   2. Something that is perpetual. --South.

   3. Endless time. ``And yet we should, for perpetuity, go
      hence in debt.'' --Shak.

   4. (Annuities)
      (a) The number of years in which the simple interest of
          any sum becomes equal to the principal.
      (b) The number of years' purchase to be given for an
          annuity to continue forever.
      (c) A perpetual annuity.

   5. (Law)
      (a) Duration without limitations as to time.
      (b) The quality or condition of an estate by which it
          becomes inalienable, either perpetually or for a very
          long period; also, the estate itself so modified or
          perpetuated.

Source : WordNet®

perpetuity
     n : the property of being perpetual (seemingly ceaseless) [syn:
         {sempiternity}]