Source : Webster's Revised Unabridged Dictionary (1913)

Ptarmigan \Ptar"mi*gan\, n. [Gael. tarmachan; cf. Ir. tarmochan,
   tarmonach.] (Zo["o]l.)
   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.

   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 ({L. Scoticus}), is reddish
         brown, and does not turn white in winter. The white, or
         willow, ptarmigan ({L. albus}) is found in both Europe
         and America.