Definition of "deer"

A ruminant mammal with antlers and hooves of the family Cervidae, or one of several similar animals from related families of the order Artiodactyla.  examples

(in particular) One of the smaller animals of this family, distinguished from a moose or elk  examples

The meat of such an animal; venison.  examples

(obsolete, except in the phrase "small deer") Any animal, especially a quadrupedal mammal as opposed to a bird, fish, etc.  quotations