The Collaborative International Dictionary of English v.0.48:

Abundance \A*bun"dance\ ([.a]*b[u^]n"dans), n. [OE.
   (h)abundaunce, abundance, F. abondance, L. abundantia, fr.
   abundare. See Abound.]
   An overflowing fullness; ample sufficiency; great plenty;
   profusion; copious supply; superfluity; wealth: -- strictly
   applicable to quantity only, but sometimes used of number.
   [1913 Webster]

         It is lamentable to remember what abundance of noble
         blood hath been shed with small benefit to the
         Christian state.                         --Raleigh.
   [1913 Webster]

   Syn: Exuberance; plenteousness; plenty; copiousness;
        overflow; riches; affluence; wealth.

   Usage: Abundance, Plenty, Exuberance. These words rise
          upon each other in expressing the idea of fullness.
          Plenty denotes a sufficiency to supply every want; as,
          plenty of food, plenty of money, etc. Abundance
          express more, and gives the idea of superfluity or
          excess; as, abundance of riches, an abundance of wit
          and humor; often, however, it only denotes plenty in a
          high degree. Exuberance rises still higher, and
          implies a bursting forth on every side, producing
          great superfluity or redundance; as, an exuberance of
          mirth, an exuberance of animal spirits, etc.
          [1913 Webster]

WordNet (r) 3.0 (2006):

abundance
    n 1: the property of a more than adequate quantity or supply;
         "an age of abundance" [syn: abundance, copiousness,
         teemingness] [ant: scarceness, scarcity]
    2: (physics) the ratio of the number of atoms of a specific
       isotope of an element to the total number of isotopes present
    3: (chemistry) the ratio of the total mass of an element in the
       earth's crust to the total mass of the earth's crust;
       expressed as a percentage or in parts per million