The Collaborative International Dictionary of English v.0.48:

Numerous \Nu"mer*ous\, a. [L. numerosus. See Number.]
   1. Consisting of a great number of units or individual
      objects; being many; as, a numerous army; numerous
      objections.
      [1913 Webster]

            Such and so numerous was their chivalry. --Milton.
      [1913 Webster]

   2. Consisting of poetic numbers; rhythmical; measured and
      counted; melodious; musical. [Obs.]
      [1913 Webster]

            Such prompt eloquence
            Flowed from their lips, in prose or numerous verse.
                                                  --Milton.
      [1913 Webster] -- Nu"mer*ous*ly, adv. --
      Nu"mer*ous*ness, n.
      [1913 Webster]

WordNet (r) 3.0 (2006):

numerous
    adj 1: amounting to a large indefinite number; "numerous times";
           "the family was numerous"; "Palomar's fans are legion"
           [syn: numerous, legion(p)]

Moby Thesaurus II by Grady Ward, 1.0:

95 Moby Thesaurus words for "numerous":
   abounding, abundant, affluent, all-sufficing, ample, aplenty, big,
   billion, bottomless, bounteous, bountiful, certain, composite,
   considerable, copious, countless, diffuse, effuse, epidemic,
   ever so many, exhaustless, extravagant, exuberant, fat, fertile,
   flush, full, full many, galore, generous, great, heaped-up,
   in plenty, in quantity, inexhaustible, jillion, large, lavish,
   legion, liberal, luxuriant, many, maximal, million, more,
   more than one, much, multifarious, multifold, multiple,
   multitudinal, multitudinous, myriad, no few, not a few,
   not singular, opulent, overflowing, plenitudinous, plenteous,
   plentiful, plenty, plural, pluralistic, plurative, populous,
   prevailing, prevalent, prodigal, productive, profuse, profusive,
   quite some, rampant, replete, rich, rife, riotous, running over,
   several, some, sundry, superabundant, teeming, thousand, various,
   very many, voluminous, wealthy, well-found, well-furnished,
   well-provided, well-stocked, wholesale, zillion