The Collaborative International Dictionary of English v.0.48:

Sky \Sky\ (sk[imac]), n.; pl. Skies (sk[imac]z). [OE. skie a
   cloud, Icel. sk[=y]; akin to Sw. & Dan. sky; cf. AS. sc[=u]a,
   sc[=u]wa, shadow, Icel. skuggi; probably from the same root
   as E. scum. [root]158. See Scum, and cf. Hide skin,
   Obscure.]
   1. A cloud. [Obs.]
      [1913 Webster]

            [A wind] that blew so hideously and high,
            That it ne lefte not a sky
            In all the welkin long and broad.     --Chaucer.
      [1913 Webster]

   2. Hence, a shadow. [Obs.]
      [1913 Webster]

            She passeth as it were a sky.         --Gower.
      [1913 Webster]

   3. The apparent arch, or vault, of heaven, which in a clear
      day is of a blue color; the heavens; the firmament; --
      sometimes in the plural.
      [1913 Webster]

            The Norweyan banners flout the sky.   --Shak.
      [1913 Webster]

   4. The wheather; the climate.
      [1913 Webster]

            Thou wert better in thy grave than to answer with
            thy uncovered body this extremity of the skies.
                                                  --Shak.
      [1913 Webster]

   Note: Sky is often used adjectively or in the formation of
         self-explaining compounds; as, sky color, skylight,
         sky-aspiring, sky-born, sky-pointing, sky-roofed, etc.
         [1913 Webster]

   Sky blue, an azure color.

   Sky scraper (Naut.), a skysail of a triangular form.
      --Totten.

   Under open sky, out of doors. "Under open sky adored."
      --Milton.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Sky \Sky\, v. t. [imp. & p. p. Skiedor Skyed; p. pr. & vb.
   n. Skying.]
   1. To hang (a picture on exhibition) near the top of a wall,
      where it can not be well seen. [Colloq.]
      [1913 Webster]

            Brother Academicians who skied his pictures. --The
                                                  Century.
      [1913 Webster]

   2. To throw towards the sky; as, to sky a ball at cricket.
      [Colloq.]
      [1913 Webster]

WordNet (r) 3.0 (2006):

sky
    n 1: the atmosphere and outer space as viewed from the earth
    v 1: throw or toss with a light motion; "flip me the beachball";
         "toss me newspaper" [syn: flip, toss, sky, pitch]

Moby Thesaurus II by Grady Ward, 1.0:

81 Moby Thesaurus words for "sky":
   Caelus, Olympian heights, acme, aerial heights, air, apex, apogee,
   azure, blue sky, brow, caelum, canopy, canopy of heaven, cap,
   cerulean, climax, cloud nine, cope, crest, crown, culmen,
   culmination, dizzy heights, edge, elevation, eminence, empyrean,
   ether, extreme limit, extremity, firmament, heaven, heavens,
   height, heights, high noon, highest pitch, highest point, hyaline,
   lift, lifts, limit, maximum, meridian, mountaintop, ne plus ultra,
   no place higher, noon, peak, pinnacle, pitch, point, pole, raise,
   ridge, rise, rising ground, seventh heaven, spire, starry heaven,
   steep, stratosphere, summit, the blue, the blue serene, tip,
   tip-top, top, upmost, upper extremity, uppermost, uprise, utmost,
   vantage ground, vantage point, vault, vault of heaven, vertex,
   very top, welkin, zenith