The Collaborative International Dictionary of English v.0.48:

Shady \Shad"y\, a. [Compar. Shadier; superl. Shadiest.]
   1. Abounding in shade or shades; overspread with shade;
      causing shade.
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            The shady trees cover him with their shadow. --Job.
                                                  xl. 22.
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            And Amaryllis fills the shady groves. --Dryden.
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   2. Sheltered from the glare of light or sultry heat.
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            Cast it also that you may have rooms shady for
            summer and warm for winter.           --Bacon.
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   3. Of or pertaining to shade or darkness; hence, unfit to be
      seen or known; of questionable character; unsavory;
      equivocal; dubious, corrupt, or criminal; as, a shady
      character; -- of people or activities. [Colloq.] "A shady
      business." --London Sat. Rev.

            Shady characters, disreputable, criminal. --London
                                                  Spectator.
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   On the shady side of, on the thither side of; as, on the
      shady side of fifty; that is, more than fifty. [Colloq.]


   To keep shady, to stay in concealment; also, to be
      reticent. [Slang]
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