PACHYDERMATOUS, a. [Gr., thick, skin.] Having a thick skin; an epithet applied to an order of animals, called Pachydermata, embracing all the hoofed quadrupeds which do not ruminate, as the elephant, mastodon or North American mammoth, hippopotamus, sus or hog, rhinoceros, tapir, and horse. The horse constitutes a separate order, Solipeda.