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]

The Collaborative International Dictionary of English v.0.48:

elk \elk\ ([e^]lk), n. [Icel. elgr; akin to Sw. elg, AS. eolh,
   OHG. elaho, MHG. elch, cf. L. alces; perh. akin to E. eland.]
   (Zo["o]l.)
   A large deer, of several species. The European elk Alces
   alces (formerly Alces machlis or Cervus alces) is
   closely allied to the American moose. The American elk, or
   wapiti (Cervus Canadensis) the largest member of the deer
   family, has large, spreading antlers and is closely related
   to the European stag. See Moose, and Wapiti.
   [1913 Webster +PJC]

   Irish elk (Paleon.), a large, extinct, Quaternary deer
      (Cervus giganteus) with widely spreading antlers. Its
      remains have been found beneath the peat of swamps in
      Ireland and England. See Illustration in Appendix; also
      Illustration of Antler.

   Cape elk (Zo["o]l.), the eland. elk

WordNet (r) 3.0 (2006):

Alces alces
    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]