noun
(countable) A ruminant mammal with hooves and often antlers, of the family Cervidae, or one of several similar animals from related families of the order Artiodactyla, such as the musk deer or mouse deer.
(uncountable) The meat of such an animal, obtained through the process of hunting or from specialized deer farms; venison.
(countable; obsolete, except in the phrase "small deer") Any animal, especially a quadrupedal mammal as opposed to a bird, fish, etc.