Innumerable, a.
Etymology: [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. Innumerable as the stars of night. Milton. -- In*nu"mer*a*ble*ness, n. -- In*nu"mer*a*bly, adv.
Shades of meaning
Fernald has no entry of its own for innumerable; he lists it under infinite.
Where he writes about it:
Countless, innumerable, and numberless, which should be the same as infinite, are in common usage vaguely employed to denote what it is difficult or practically impossible to count or number, tho perhaps falling far short of infinite; as, countless leaves, the countless sands on the seashore, numberless battles, innumerable delays. — from infinite