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:

Partridge \Par"tridge\ (p[aum]r"tr[i^]j), n. [OE. partriche,
   pertriche, OF. pertris, perdriz, F. perdrix, L. perdix,
   -icis, fr. Gr. pe`rdix.] (Zool.)
   1. Any one of numerous species of small gallinaceous birds of
      the genus Perdix and several related genera of the
      family Perdicid[ae], of the Old World. The partridge is
      noted as a game bird.
      [1913 Webster]

            Full many a fat partrich had he in mew. --Chaucer.
      [1913 Webster]

   Note: The common European, or gray, partridge (Perdix
         cinerea) and the red-legged partridge (Caccabis
         rubra) of Southern Europe and Asia are well-known
         species.
         [1913 Webster]

   2. Any one of several species of quail-like birds belonging
      to Colinus, and allied genera. [U.S.]
      [1913 Webster]

   Note: Among them are the bobwhite (Colinus Virginianus) of
         the Eastern States; the plumed, or mountain, partridge
         (Oreortyx pictus) of California; the Massena
         partridge (Cyrtonyx Montezum[ae]); and the California
         partridge (Callipepla Californica).
         [1913 Webster]

   3. The ruffed grouse (Bonasa umbellus). [New Eng.]
      [1913 Webster]

   Bamboo partridge (Zool.), a spurred partridge of the genus
      Bambusicola. Several species are found in China and the
      East Indies.

   Night partridge (Zool.), the woodcock. [Local, U.S.]

   Painted partridge (Zool.), a francolin of South Africa
      (Francolinus pictus).

   Partridge berry. (Bot.)
      (a) The scarlet berry of a trailing american plant
          (Mitchella repens) of the order Rubiace[ae],
          having roundish evergreen leaves, and white fragrant
          flowers sometimes tinged with purple, growing in pairs
          with the ovaries united, and producing the berries
          which remain over winter; also, the plant itself.
      (b) The fruit of the creeping wintergreen (Gaultheria
          procumbens); also, the plant itself.

   Partridge dove (Zool.) Same as Mountain witch, under
      Mountain.

   Partridge pea (Bot.), a yellow-flowered leguminous herb
      (Cassia Cham[ae]crista), common in sandy fields in the
      Eastern United States.

   Partridge shell (Zool.), a large marine univalve shell
      (Dolium perdix), having colors variegated like those of
      the partridge.

   Partridge wood
      (a) A variegated wood, much esteemed for cabinetwork. It
          is obtained from tropical America, and one source of
          it is said to be the leguminous tree Andira inermis.
          Called also pheasant wood.
      (b) A name sometimes given to the dark-colored and
          striated wood of some kind of palm, which is used for
          walking sticks and umbrella handles.

   Sea partridge (Zool.), an Asiatic sand partridge
      (Ammoperdix Bonhami); -- so called from its note.

   Snow partridge (Zool.), a large spurred partridge (Lerwa
      nivicola) which inhabits the high mountains of Asia;
      called also jermoonal.

   Spruce partridge. See under Spruce.

   Wood partridge, or Hill partridge (Zool.), any small
      Asiatic partridge of the genus Arboricola.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Ruffed \Ruffed\, a.
   Furnished with a ruff.
   [1913 Webster]

   Ruffed grouse (Zool.), a North American grouse (Bonasa
      umbellus) common in the wooded districts of the Northern
      United States. The male has a ruff of brown or black
      feathers on each side of the neck, and is noted for the
      loud drumming sound he makes during the breeding season.
      Called also tippet grouse, partridge, birch
      partridge, pheasant, drummer, and white-flesher.

   ruffed lemur (Zool.), a species of lemur (lemur varius)
      having a conspicuous ruff on the sides of the head. Its
      color is varied with black and white. Called also ruffed
      maucaco.
      [1913 Webster]

WordNet (r) 3.0 (2006):

Bonasa umbellus
    n 1: valued as a game bird in eastern United States and Canada
         [syn: ruffed grouse, partridge, Bonasa umbellus]