The Collaborative International Dictionary of English v.0.48:

Grayhound \Gray"hound`\ (-hound`), n. (Zool.)
   See Greyhound.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Greyhound \Grey"hound`\, n. [OE. graihund, greihound, greahund,
   grihond, Icel. greyhundr; grey greyhound + hundr dog; cf. AS.
   gr[imac]ghund. The origin of the first syllable is unknown.]
   1. A slender, graceful breed of dogs, remarkable for keen
      sight and swiftness. It is one of the oldest varieties
      known, and is figured on the Egyptian monuments. [Written
      also grayhound.]
      [1913 Webster]

   2. A swift steamer, esp. an ocean steamer.
      [Webster 1913 Suppl.]