n. any vertebrate of the class Mammalia, usu. a warm-blooded quadruped with hair or fur, the females of which possess milk-secreting mammae for the nourishment of the young, and including human beings, dogs, rabbits, whales, etc. mammalian adj. & n. mammalogy n.
[ mod.L mammalia neut. pl. of L mammalis (as MAMMA(2)) ]