What does "shady" mean?

Additional senses

1. 2.Sheltered from the glare of light or sultry heat. Cast it also that you may have rooms shady for summer and warm for winter. Bacon.
2. 3.Of or pertaining to shade or darkness; hence, unfit to be seen or known; equivocal; dubious or corrupt. [Colloq.] "A shady business." London Sat. Rev. Shady characters, disreputable, criminal. London Spectator. 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]