The Collaborative International Dictionary of English v.0.48:

Gray \Gray\ (gr[=a]), a. [Compar. Grayer; superl. Grayest.]
   [OE. gray, grey, AS. gr[=ae]g, gr[=e]g; akin to D. graauw,
   OHG. gr[=a]o, G. grau, Dan. graa, Sw. gr[*a], Icel. gr[=a]r.]
   [Written also grey.]
   1. any color of neutral hue between white and black; white
      mixed with black, as the color of pepper and salt, or of
      ashes, or of hair whitened by age; sometimes, a dark mixed
      color; as, the soft gray eye of a dove.
      [1913 Webster]

            These gray and dun colors may be also produced by
            mixing whites and blacks.             --Sir I.
                                                  Newton.
      [1913 Webster]

   2. Gray-haired; gray-headed; of a gray color; hoary.
      [1913 Webster]

   3. Old; mature; as, gray experience. -- Ames.
      [1913 Webster]

   4. gloomy; dismal.
      [PJC]

   Gray antimony (Min.), stibnite.

   Gray buck (Zool.), the chickara.

   Gray cobalt (Min.), smaltite.

   Gray copper (Min.), tetrahedrite.

   Gray duck (Zool.), the gadwall; also applied to the female
      mallard.

   Gray falcon (Zool.) the peregrine falcon.

   Gray Friar. See Franciscan, and Friar.

   Gray hen (Zool.), the female of the blackcock or black
      grouse. See Heath grouse.

   Gray mill or Gray millet (Bot.), a name of several plants
      of the genus Lithospermum; gromwell.

   Gray mullet (Zool.) any one of the numerous species of the
      genus Mugil, or family Mugilid[ae], found both in the
      Old World and America; as the European species
      (Mugilid[ae] capito, and Mugilid[ae] auratus), the
      American striped mullet (Mugilid[ae] albula), and the
      white or silver mullet (Mugilid[ae] Braziliensis). See
      Mullet.

   Gray owl (Zool.), the European tawny or brown owl (Syrnium
      aluco). The great gray owl (Ulula cinerea) inhabits
      arctic America.

   Gray parrot (Zool.), an African parrot (Psittacus
      erithacus), very commonly domesticated, and noted for its
      aptness in learning to talk. Also called jako.

   Gray pike. (Zool.) See Sauger.

   Gray snapper (Zool.), a Florida fish; the sea lawyer. See
      Snapper.

   Gray snipe (Zool.), the dowitcher in winter plumage.

   Gray whale (Zool.), a rather large and swift whale of the
      northern Pacific (Eschrichtius robustus, formerly
      Rhachianectes glaucus), having short jaws and no dorsal
      fin. It grows to a length of 50 feet (someimes 60 feet).
      It was formerly taken in large numbers in the bays of
      California, and is now rare; -- called also grayback,
      devilfish, and hardhead. It lives up to 50 or 60 years
      and adults weigh from 20 to 40 tons.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Heath \Heath\ (h[=e]th), n. [OE. heth waste land, the plant
   heath, AS. h[=ae][eth]; akin to D. & G. heide, Icel.
   hei[eth]r waste land, Dan. hede, Sw. hed, Goth. hai[thorn]i
   field, L. bucetum a cow pasture; cf. W. coed a wood, Skr.
   ksh[=e]tra field. [root]20.]
   1. (Bot.)
      (a) A low shrub (Erica vulgaris or Calluna vulgaris),
          with minute evergreen leaves, and handsome clusters of
          pink flowers. It is used in Great Britain for brooms,
          thatch, beds for the poor, and for heating ovens. It
          is also called heather, and ling.
      (b) Also, any species of the genus Erica, of which
          several are European, and many more are South African,
          some of great beauty. See Illust. of Heather.
          [1913 Webster]

   2. A place overgrown with heath; any cheerless tract of
      country overgrown with shrubs or coarse herbage.
      [1913 Webster]

            Their stately growth, though bare,
            Stands on the blasted heath.          --Milton
      [1913 Webster]

   Heath cock (Zool.), the blackcock. See Heath grouse
      (below).

   Heath grass (Bot.), a kind of perennial grass, of the genus
      Triodia (Triodia decumbens), growing on dry heaths.

   Heath grouse, or Heath game (Zool.), a European grouse
      (Tetrao tetrix), which inhabits heaths; -- called also
      black game, black grouse, heath poult, heath fowl,
      moor fowl. The male is called heath cock, and
      blackcock; the female, heath hen, and gray hen.

   Heath hen. (Zool.) See Heath grouse (above).

   Heath pea (Bot.), a species of bitter vetch (Lathyrus
      macrorhizus), the tubers of which are eaten, and in
      Scotland are used to flavor whisky.

   Heath throstle (Zool.), a European thrush which frequents
      heaths; the ring ouzel.
      [1913 Webster]

WordNet (r) 3.0 (2006):

gray hen
    n 1: female black grouse [syn: greyhen, grayhen, grey hen,
         gray hen, heath hen]