Source : Webster's Revised Unabridged Dictionary (1913)

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.

            Such and so numerous was their chivalry. --Milton.

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

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

Source : WordNet®

numerousness
     n : a large number [syn: {numerosity}, {multiplicity}]