Source : Webster's Revised Unabridged Dictionary (1913)

Deer \Deer\ (d[=e]r), n. sing. & pl. [OE. der, deor, animal,
   wild animal, AS. de['o]r; akin to D. dier, OFries. diar, G.
   thier, tier, Icel. d[=y]r, Dan. dyr, Sw. djur, Goth. dius; of
   unknown origin. [root]71.]
   1. Any animal; especially, a wild animal. [Obs.] --Chaucer.

            Mice and rats, and such small deer.   --Shak.

            The camel, that great deer.           --Lindisfarne
                                                  MS.

   2. (Zo["o]l.) A ruminant of the genus {Cervus}, of many
      species, and of related genera of the family {Cervid[ae]}.
      The males, and in some species the females, have solid
      antlers, often much branched, which are shed annually.
      Their flesh, for which they are hunted, is called venison.

   Note: The deer hunted in England is {Cervus elaphus}, called
         also stag or red deer; the fallow deer is {C. dama};
         the common American deer is {C. Virginianus}; the
         blacktailed deer of Western North America is {C.
         Columbianus}; and the mule deer of the same region is
         {C. macrotis}. See {Axis}, {Fallow deer}, {Mule deer},
         {Reindeer}.

   Note: Deer is much used adjectively, or as the first part of
         a compound; as, deerkiller, deerslayer, deerslaying,
         deer hunting, deer stealing, deerlike, etc.

   {Deer mouse} (Zo["o]l.), the white-footed mouse ({Hesperomys
      leucopus}) of America.

   {Small deer}, petty game, not worth pursuing; -- used
      metaphorically. (See citation from Shakespeare under the
      first definition, above.) ``Minor critics . . . can find
      leisure for the chase of such small deer.'' --G. P. Marsh.

Source : WordNet®

deer
     n : distinguished from Bovidae by the male's having solid
         deciduous antlers [syn: {cervid}]