The Collaborative International Dictionary of English v.0.48:

Shade \Shade\ (sh[=a]d), n. [OE. shade, shadewe, schadewe, AS.
   sceadu, scead; akin to OS. skado, D. schaduw, OHG. scato,
   (gen. scatewes), G. schatten, Goth. skadus, Ir. & Gael.
   sgath, and probably to Gr. sko`tos darkness. [root]162. Cf.
   Shadow, Shed a hat.]
   1. Comparative obscurity owing to interception or
      interruption of the rays of light; partial darkness caused
      by the intervention of something between the space
      contemplated and the source of light.
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   Note: Shade differs from shadow as it implies no particular
         form or definite limit; whereas a shadow represents in
         form the object which intercepts the light. When we
         speak of the shade of a tree, we have no reference to
         its form; but when we speak of measuring a pyramid or
         other object by its shadow, we have reference to its
         form and extent.
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   2. Darkness; obscurity; -- often in the plural.
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            The shades of night were falling fast. --Longfellow.
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   3. An obscure place; a spot not exposed to light; hence, a
      secluded retreat.
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            Let us seek out some desolate shade, and there
            Weep our sad bosoms empty.            --Shak.
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   4. That which intercepts, or shelters from, light or the
      direct rays of the sun; hence, also, that which protects
      from heat or currents of air; a screen; protection;
      shelter; cover; as, a lamp shade.
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            The Lord is thy shade upon thy right hand. --Ps.
                                                  cxxi. 5.
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            Sleep under a fresh tree's shade.     --Shak.
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            Let the arched knife well sharpened now assail the
            spreading shades of vegetables.       --J. Philips.
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   5. Shadow. [Poetic.]
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            Envy will merit, as its shade, pursue. --Pope.
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   6. The soul after its separation from the body; -- so called
      because the ancients it to be perceptible to the sight,
      though not to the touch; a spirit; a ghost; as, the shades
      of departed heroes.
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            Swift as thought the flitting shade
            Thro' air his momentary journey made. --Dryden.
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   7. (Painting, Drawing, etc.) The darker portion of a picture;
      a less illuminated part. See Def. 1, above.
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   8. Degree or variation of color, as darker or lighter,
      stronger or paler; as, a delicate shade of pink.
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            White, red, yellow, blue, with their several
            degrees, or shades and mixtures, as green only in by
            the eyes.                             --Locke.
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   9. A minute difference or variation, as of thought, belief,
      expression, etc.; also, the quality or degree of anything
      which is distinguished from others similar by slight
      differences; as, the shades of meaning in synonyms.
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            New shades and combinations of thought. --De
                                                  Quincey.
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            Every shade of religious and political opinion has
            its own headquarters.                 --Macaulay.
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   The Shades, the Nether World; the supposed abode of souls
      after leaving the body.
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The Collaborative International Dictionary of English v.0.48:

Shade \Shade\, v. t. [imp. & p. p. Shaded; p. pr. & vb. n.
   Shading.]
   1. To shelter or screen by intercepting the rays of light; to
      keep off illumination from. --Milton.
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            I went to crop the sylvan scenes,
            And shade our altars with their leafy greens.
                                                  --Dryden.
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   2. To shelter; to cover from injury; to protect; to screen;
      to hide; as, to shade one's eyes.
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            Ere in our own house I do shade my head. --Shak.
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   3. To obscure; to dim the brightness of.
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            Thou shad'st
            The full blaze of thy beams.          --Milton.
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   4. To pain in obscure colors; to darken.
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   5. To mark with gradations of light or color.
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   6. To present a shadow or image of; to shadow forth; to
      represent. [Obs.]
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            [The goddess] in her person cunningly did shade
            That part of Justice which is Equity. --Spenser.
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The Collaborative International Dictionary of English v.0.48:

Shade \Shade\ (sh[=a]d), v. i. [See Shade, n.]
   To undergo or exhibit minute difference or variation, as of
   color, meaning, expression, etc.; to pass by slight changes;
   -- used chiefly with a preposition, as into, away, off.

         This small group will be most conveniently treated with
         the emotional division, into which it shades. --Edmund
                                                  Gurney.
   [Webster 1913 Suppl.]

WordNet (r) 3.0 (2006):

shade
    n 1: relative darkness caused by light rays being intercepted by
         an opaque body; "it is much cooler in the shade"; "there's
         too much shadiness to take good photographs" [syn: shade,
         shadiness, shadowiness]
    2: a quality of a given color that differs slightly from another
       color; "after several trials he mixed the shade of pink that
       she wanted" [syn: shade, tint, tincture, tone]
    3: protective covering that protects something from direct
       sunlight; "they used umbrellas as shades"; "as the sun moved
       he readjusted the shade"
    4: a subtle difference in meaning or opinion or attitude;
       "without understanding the finer nuances you can't enjoy the
       humor"; "don't argue about shades of meaning" [syn: nuance,
       nicety, shade, subtlety, refinement]
    5: a position of relative inferiority; "an achievement that puts
       everything else in the shade"; "his brother's success left
       him in the shade"
    6: a slight amount or degree of difference; "a tad too
       expensive"; "not a tad of difference"; "the new model is a
       shade better than the old one" [syn: tad, shade]
    7: a mental representation of some haunting experience; "he
       looked like he had seen a ghost"; "it aroused specters from
       his past" [syn: ghost, shade, spook, wraith,
       specter, spectre]
    8: a representation of the effect of shadows in a picture or
       drawing (as by shading or darker pigment)
    v 1: cast a shadow over [syn: shadow, shade, shade off]
    2: represent the effect of shade or shadow on [syn: shade,
       fill in]
    3: protect from light, heat, or view; "Shade your eyes when you
       step out into the bright sunlight"
    4: vary slightly; "shade the meaning"
    5: pass from one quality such as color to another by a slight
       degree; "the butterfly wings shade to yellow"