Source : Webster's Revised Unabridged Dictionary (1913)

Mammal \Mam"mal\, n.; pl. {Mammals}. [L. mammalis belonging to
   the breast, fr. mamma the breast or pap: cf. F. mammal.]
   (Zo["o]l.)
   One of the Mammalia.

   {Age of mammals}. See under {Age}, n., 8.

Source : WordNet®

mammal
     n : any warm-blooded vertebrate having the skin more or less
         covered with hair; young are born alive except for the
         small subclass of monotremes and nourished with milk