The Collaborative International Dictionary of English v.0.48:

Abundant \A*bun"dant\, a. [OE. (h)abundant, aboundant, F.
   abondant, fr. L. abudans, p. pr. of abundare. See Abound.]
   Fully sufficient; plentiful; in copious supply; -- followed
   by in, rarely by with. "Abundant in goodness and truth."
   --Exod. xxxiv. 6.
   [1913 Webster]

   Abundant number (Math.), a number, the sum of whose aliquot
      parts exceeds the number itself. Thus, 1, 2, 3, 4, 6, the
      aliquot parts of 12, make the number 16. This is opposed
      to a deficient number, as 14, whose aliquot parts are 1,
      2, 7, the sum of which is 10; and to a perfect number,
      which is equal to the sum of its aliquot parts, as 6,
      whose aliquot parts are 1, 2., 3.
      [1913 Webster]

   Syn: Ample; plentiful; copious; plenteous; exuberant;
        overflowing; rich; teeming; profuse; bountiful; liberal.
        See Ample.
        [1913 Webster]

WordNet (r) 3.0 (2006):

abundant
    adj 1: present in great quantity; "an abundant supply of water"
           [ant: scarce]

Moby Thesaurus II by Grady Ward, 1.0:

91 Moby Thesaurus words for "abundant":
   abounding, affluent, all-sufficing, ample, aplenty, blooming,
   bottomless, bounteous, bountiful, bursting, bursting out, common,
   copious, countless, crammed, creative, crowded, diffuse, diffusive,
   effuse, effusive, epidemic, exhaustless, extravagant, exuberant,
   fat, fecund, fertile, flourishing, flush, formless, fructiferous,
   fruitful, full, full of, galore, generous, gushing, gushy,
   in good supply, in plenty, in quantity, inexhaustible, lavish,
   liberal, lush, luxuriant, many, maximal, much, multitudinous,
   numerous, opulent, overflowing, plenitudinous, plenteous,
   plentiful, plenty, pleonastic, pregnant, prevailing, prevalent,
   prodigal, productive, profuse, profusive, proliferous, prolific,
   rampant, redundant, reiterative, repetitive, replete, rich, rife,
   riotous, running over, seminal, superabundant, swarming,
   tautologous, teeming, thick, thriving, uberous, wealthy,
   well-found, well-furnished, well-provided, well-stocked,
   wholesale