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):

innumerable
    adj 1: too numerous to be counted; "incalculable riches";
           "countless hours"; "an infinite number of reasons";
           "innumerable difficulties"; "the multitudinous seas";
           "myriad stars"; "untold thousands" [syn: countless,
           infinite, innumerable, innumerous, multitudinous,
           myriad, numberless, uncounted, unnumberable,
           unnumbered, unnumerable]

Moby Thesaurus II by Grady Ward, 1.0:

44 Moby Thesaurus words for "innumerable":
   all-comprehensive, all-inclusive, boundless, countless, endless,
   eternal, exhaustless, extending everywhere, illimitable, illimited,
   immeasurable, immense, incalculable, incomprehensible,
   inexhaustible, infinite, infinitely continuous, interminable,
   interminate, limitless, measureless, no end of, numberless,
   perpetual, shoreless, sumless, termless, unbounded,
   uncircumscribed, uncountable, uncounted, unfathomable, universal,
   unlimited, unmeasurable, unmeasured, unnumbered, unplumbed, untold,
   without bound, without end, without limit, without measure,
   without number