The Collaborative International Dictionary of English v.0.48:

Innumerable \In*nu`mer*a*ble\, a. [L. innumerabilis : cf. F.
   innumefable. See In- not, and Numerable.]
   Not capable of being counted, enumerated, or numbered, for
   multitude; countless; numberless; unnumbered, hence,
   indefinitely numerous; of great number.
   [1913 Webster]

         Innumerable as the stars of night.       --Milton.
   -- In*nu"mer*a*ble*ness, n. -- In*nu"mer*a*bly, adv.
   [1913 Webster]

WordNet (r) 3.0 (2006):

innumerableness
    n 1: a number beyond counting [syn: innumerableness,
         countlessness]