The Collaborative International Dictionary of English v.0.48:

Mammal \Mam"mal\, n.; pl. Mammals. [L. mammalis belonging to
   the breast, fr. mamma the breast or pap: cf. F. mammal.]
   (Zool.)
   One of the Mammalia.
   [1913 Webster]

   Age of mammals. See under Age, n., 8.
      [1913 Webster]

WordNet (r) 3.0 (2006):

mammal
    n 1: 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 [syn:
         mammal, mammalian]

Moby Thesaurus II by Grady Ward, 1.0:

286 Moby Thesaurus words for "mammal":
   Angora goat, Arctic fox, Belgian hare, Caffre cat, Indian buffalo,
   Kodiak bear, Reptilia, Virginia deer, aardvark, aardwolf, alpaca,
   amphibian, anteater, antelope, antelope chipmunk, aoudad, apar,
   aquatic, armadillo, ass, aurochs, badger, bandicoot, bassarisk,
   bat, bear, beaver, bettong, binturong, biped, bison, black bear,
   black buck, black cat, black fox, black sheep, blue fox, bobcat,
   brown bear, brush deer, brush wolf, buffalo, buffalo wolf, burro,
   burro deer, cachalot, camel, camelopard, canine, cannibal,
   capybara, carabao, caribou, carnivore, carpincho, cat,
   cat-a-mountain, catamount, cattalo, cavy, chamois, cheetah,
   chevrotain, chinchilla, chipmunk, cinnamon bear, coon, coon cat,
   cosmopolite, cotton mouse, cotton rat, cougar, cow, coyote, coypu,
   deer, deer tiger, dingo, dog, donkey, dormouse, dromedary, echidna,
   eland, elephant, elk, ermine, eyra, fallow deer, feline, ferret,
   field mouse, fisher, fitch, flying phalanger, foumart, fox,
   fox squirrel, gazelle, gemsbok, genet, giraffe, glutton, gnawer,
   gnu, gnu goat, goat, goat antelope, gopher, grizzly bear,
   ground squirrel, groundhog, guanaco, guinea pig, hamster, hare,
   harnessed antelope, hartebeest, hedgehog, herbivore, hippopotamus,
   hog, horse, hyena, hyrax, ibex, insectivore, invertebrate, jackal,
   jackass, jackrabbit, jaguar, jaguarundi, jerboa, jerboa kangaroo,
   kaama, kangaroo, kangaroo mouse, kangaroo rat, karakul, kinkajou,
   kit fox, koala, lapin, lemming, leopard, leopard cat, lion, llama,
   lynx, mammalian, mammoth, mara, marmot, marsupial, marsupialian,
   marten, mastodon, meerkat, mink, mole, mongoose, moose, mouflon,
   mountain goat, mountain lion, mountain sheep, mouse, mule,
   mule deer, muntjac, musk deer, musk hog, musk-ox, muskrat,
   musquash, nilgai, nutria, ocelot, okapi, omnivore, onager, oont,
   opossum, otter, ounce, ox, pack rat, painter, panda, pangolin,
   panther, peccary, peludo, phalanger, pig, pine mouse, platypus,
   pocket gopher, pocket mouse, pocket rat, polar bear, polar fox,
   polecat, porcupine, possum, pouched rat, poyou, prairie dog,
   prairie wolf, primate, pronghorn, puma, quadruped, rabbit, raccoon,
   rat, red deer, red squirrel, reindeer, reptile, rhinoceros, rodent,
   roe, roe deer, roebuck, ruminant, sable, scavenger, serval, sheep,
   shrew, shrew mole, sika, silver fox, skunk, sloth, snowshoe rabbit,
   springbok, squirrel, stoat, suslik, swamp rabbit, swine, takin,
   tamandua, tamarin, tapir, tarpan, tatou, tatou peba, tatouay,
   tiger, tiger cat, timber wolf, tree shrew, ungulate, urus, varmint,
   vermin, vertebrate, vole, wallaby, warthog, water buffalo,
   waterbuck, weasel, wharf rat, whistler, white fox, wild ass,
   wild boar, wild goat, wild ox, wildcat, wildebeest, wolf,
   wolverine, wombat, wood rat, woodchuck, woolly mammoth, yak, zebra,
   zebu, zoril