The Collaborative International Dictionary of English v.0.48:

Shadowy \Shad"ow*y\, a.
   1. Full of shade or shadows; causing shade or shadow.
      "Shadowy verdure." --Fenton.
      [1913 Webster]

            This shadowy desert, unfrequented woods. --Shak.
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   2. Hence, dark; obscure; gloomy; dim. "The shadowy past."
      --Longfellow.
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   3. Not brightly luminous; faintly light.
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            The moon . . . with more pleasing light,
            Shadowy sets off the face things.     --Milton.
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   4. Faintly representative; hence, typical.
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            From shadowy types to truth, from flesh to spirit.
                                                  --Milton.
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   5. Unsubstantial; unreal; as, shadowy honor.
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            Milton has brought into his poems two actors of a
            shadowy
            and fictitious nature, in the persons of Sin and
            Death.                                --Addison.
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WordNet (r) 3.0 (2006):

shadowy
    adj 1: filled with shade; "the shady side of the street"; "the
           surface of the pond is dark and shadowed"; "we sat on
           rocks in a shadowy cove"; "cool umbrageous woodlands"
           [syn: shady, shadowed, shadowy, umbrageous]
    2: lacking clarity or distinctness; "a dim figure in the
       distance"; "only a faint recollection"; "shadowy figures in
       the gloom"; "saw a vague outline of a building through the
       fog"; "a few wispy memories of childhood" [syn: dim,
       faint, shadowy, vague, wispy]
    3: lacking in substance; "strange fancies of unreal and shadowy
       worlds"- W.A.Butler; "dim shadowy forms"; "a wraithlike
       column of smoke" [syn: shadowy, wraithlike]

Moby Thesaurus II by Grady Ward, 1.0:

167 Moby Thesaurus words for "shadowy":
   air-built, airy, aleatoric, aleatory, amorphous, asomatous, astral,
   blear, bleared, bleary, blind, blobby, blurred, blurry, bodiless,
   bosky, bowery, broad, cadaverous, chance, chancy, chaotic,
   chimerical, clear as mud, cloud-built, cloudy, confused,
   corpselike, dark, darkling, deathlike, decarnate, decarnated, dim,
   discarnate, disembodied, disordered, dreamlike, dusky, ectoplasmic,
   ethereal, etheric, extramundane, faint, fancied, fanciful,
   fatuitous, fatuous, feeble, filmy, fleeting, foggy, fuzzy, gaseous,
   general, ghostish, ghostlike, ghostly, ghosty, gloomy, gossamery,
   half-seen, half-visible, hallucinatory, hazy, hit-or-miss,
   ill-defined, illusory, imaginary, imagined, immaterial, impalpable,
   imponderable, imprecise, inaccurate, inchoate, incoherent,
   inconspicuous, incorporate, incorporeal, indecisive, indefinable,
   indefinite, indeterminable, indeterminate, indistinct,
   indistinguishable, inexact, insubstantial, intangible, lax, leafy,
   loose, low-profile, merely glimpsed, misty, muddy, murky, nebulous,
   nonmaterial, nonphysical, nonspecific, notional, obscure,
   obumbrate, obumbrated, occult, opaque, orderless, otherworldly,
   out of focus, overshaded, overshadowed, pale, penumbral,
   phantasmal, phantasmic, phantom, phantomic, phantomlike, psychic,
   random, rarefied, semivisible, shaded, shadow, shadowed forth,
   shady, shapeless, specterlike, spectral, spiritual, spirituous,
   stochastic, subtile, subtle, supernatural, sweeping, tenuous,
   transcendent, transitory, transmundane, umbral, uncertain, unclear,
   undefined, undestined, undetermined, unearthly, unembodied,
   unextended, unfleshly, unphysical, unplain, unreal, unrecognizable,
   unspecified, unsubstantial, unworldly, vague, vaporous, veiled,
   visionary, weak, windy, wraithlike, wraithy