The Collaborative International Dictionary of English v.0.48:

Grouse \Grouse\ (grous), n. sing. & pl. [Prob. after the analogy
   of mouse, mice, fr. the earlier grice, OF. griesche meor hen:
   cf. F. piegri[`e]che shrike.] (Zool.)
   Any of the numerous species of gallinaceous birds of the
   family Tetraonid[ae], and subfamily Tetraonin[ae],
   inhabiting Europe, Asia, and North America. They have plump
   bodies, strong, well-feathered legs, and usually mottled
   plumage. The group includes the ptarmigans (Lagopus),
   having feathered feet.
   [1913 Webster]

   Note: Among the European species are the red grouse (Lagopus
         Scoticus) and the hazel grouse (Bonasa betulina).
         See Capercaidzie, Ptarmigan, and Heath grouse.
         Among the most important American species are the
         ruffed grouse, or New England partridge (Bonasa
         umbellus); the sharp-tailed grouse (Pedioc[ae]tes
         phasianellus) of the West; the dusky blue, or pine
         grouse (Dendragapus obscurus) of the Rocky Mountains;
         the Canada grouse, or spruce partridge (D.
         Canadensis). See also Prairie hen, and Sage cock.
         The Old World sand grouse (Pterocles, etc.) belong to
         a very different family. See Pterocletes, and Sand
         grouse.
         [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Ptarmigan \Ptar"mi*gan\, n. [Gael. tarmachan; cf. Ir. tarmochan,
   tarmonach.] (Zool.)
   Any grouse of the genus Lagopus, of which numerous species
   are known. The feet are completely feathered. Most of the
   species are brown in summer, but turn white, or nearly white,
   in winter.
   [1913 Webster]

   Note: They chiefly inhabit the northern countries and high
         mountains of Europe, Asia, and America. The common
         European species is Lagopus mutus. The Scotch grouse,
         red grouse, or moor fowl (Lagopus Scoticus), is
         reddish brown, and does not turn white in winter. The
         white, or willow, ptarmigan (Lagopus albus) is found
         in both Europe and America.
         [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

moorfowl \moorfowl\, moor fowl \moor fowl\n. (Zool.)
   1. A reddish-brown grouse (Lagopus Scoticus) of upland
      moors of Great Britain; the European ptarmigan, or red
      grouse, also called the moorgame.

   Syn: red grouse, moorbird, moorgame, Lagopus scoticus.
        [WordNet 1.5]

   2. The European heath grouse. See under Heath.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

moorgame \moorgame\ n. (Zool.)
   The moorfowl.

   Syn: red grouse,, moorbird, Lagopus scoticus.
        [WordNet 1.5]

WordNet (r) 3.0 (2006):

Lagopus scoticus
    n 1: reddish-brown grouse of upland moors of Great Britain [syn:
         red grouse, moorfowl, moorbird, moor-bird,
         moorgame, Lagopus scoticus]