The Collaborative International Dictionary of English v.0.48:

moose \moose\ (m[=oo]s), n. [A native name; Knisteneaux mouswah;
   Algonquin monse. Mackenzie.]
   1. (Zool.) A large cervine mammal (Alces alces syn. Alces
      machlis, syn Alces Americanus), native of the Northern
      United States and Canada. The adult male is about as large
      as a horse, and has very large, palmate antlers. It
      closely resembles the European elk, and by many Zoologists
      is considered the same species. See Elk.
      [1913 Webster]

   2. A member of the Progressive Party; a Bull Moose.
      [Obsolescent. Cant, from the early 1900's.]
      [Webster 1913 Suppl. +PJC]

   2. [capitalized] A member of the fraternal organization named
      Loyal Order of Moose.
      [PJC]

   Moose bird (Zool.), the Canada jayor whisky jack. See
      Whisky jack.

   Moose deer. Same as Moose.

   Moose yard (Zool.), a locality where moose, in winter, herd
      together in a forest to feed and for mutual protection.
      [1913 Webster]

WordNet (r) 3.0 (2006):

moose
    n 1: large northern deer with enormous flattened antlers in the
         male; called `elk' in Europe and `moose' in North America
         [syn: elk, European elk, moose, Alces alces]