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]