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

Moby Thesaurus II by Grady Ward, 1.0:

179 Moby Thesaurus words for "abundance":
   accumulation, acres, adequacy, affluence, amassment,
   ample sufficiency, ampleness, amplitude, avalanche, backlog, bags,
   barrels, bonanza, bountifulness, bountiousness, budget,
   bumper crop, bushel, cloud of words, collection, commissariat,
   commissary, competence, copiousness, cornucopia, countlessness,
   cumulation, diffuseness, diffusion, diffusiveness, dump, ease,
   easy street, effusion, effusiveness, enough, excess, extravagance,
   exuberance, fecundity, fertility, flood, flow, fluency, foison,
   formlessness, fructiferousness, fruitfulness, full measure,
   fullness, generosity, generousness, glut, great abundance,
   great plenty, gush, gushing, heap, hoard, infinitude,
   innumerability, inventory, landslide, larder, lavishness,
   liberality, liberalness, load, logorrhea, lots, lushness,
   luxuriance, macrology, manyness, mass, material, materials,
   materiel, maximum, more than enough, mountain, much,
   multifariousness, multifoldness, multiplicity, multitude,
   multitudinousness, munitions, myriad, myriads, nimiety,
   numerousness, ocean, oceans, opulence, opulency, outpour,
   outpouring, overflow, oversupply, palilogy, peck, pile, plenitude,
   plenteousness, plentifulness, plenty, pleonasm, pregnancy,
   prevalence, procreativeness, prodigality, productive capacity,
   productiveness, productivity, profuseness, profusion, prolificacy,
   prolificity, prosperousness, provisionment, provisions, quantities,
   quantity, rampancy, rankness, rations, redundancy, reiteration,
   reiterativeness, repertoire, repertory, repetition for effect,
   repetitiveness, repleteness, repletion, rich harvest, rich vein,
   richness, rick, rifeness, riot, riotousness, satiety, scads, sea,
   shower, spate, stack, stock, stock-in-trade, stockpile, store,
   stores, stream, substantiality, substantialness, sufficiency,
   superabundance, superfluity, superflux, supplies, supply on hand,
   surplus, swarmingness, talkativeness, tautology, teeming womb,
   teemingness, thriving, tirade, tons, treasure, treasury, volume,
   wealth, well-being, world, worlds