The Collaborative International Dictionary of English v.0.48:

Quadruped \Quad"ru*ped\, a. [L. quadrupes, -pedis; quattuor four
   + pes, pedis, a foot: cf. F. quadrup[`e]de. See Quadrate,
   and Foot.]
   Having four feet.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Quadruped \Quad"ru*ped\, n. (Zool.)
   An animal having four feet, as most mammals and reptiles; --
   often restricted to the mammals.
   [1913 Webster]

WordNet (r) 3.0 (2006):

quadruped
    adj 1: having four feet [syn: quadrupedal, quadruped, four-
           footed] [ant: biped, bipedal, two-footed]
    n 1: an animal especially a mammal having four limbs specialized
         for walking

Moby Thesaurus II by Grady Ward, 1.0:

41 Moby Thesaurus words for "quadruped":
   amphibian, aquatic, biped, biquadratic, canine, cannibal,
   carnivore, cosmopolite, feline, four, four-legged, four-rayed,
   foursquare, gnawer, herbivore, insectivore, invertebrate, mammal,
   mammalian, marsupial, marsupialian, omnivore, primate, quadric,
   quadrilateral, quadrinomial, quadrivalent, quartic, quartile,
   quaternary, reptile, rodent, ruminant, scavenger, tetractinal,
   tetrad, tetravalent, ungulate, varmint, vermin, vertebrate