mustang Feral horse of the Great Plains of the USA, descended from horses that were imported from Spain. The mustang has short ears, a low-set tail and round leg bones. During the 17th century, there were 2–4 million mustangs. Today, only c.20,000 survive in sw USA.

mustang wild horse of the American plains XIX. app. blending of Sp. mestengo (now mesten̄o) and mostrenco, both applied to wild or masterless cattle, the former being f. mesta (:-L. mixta, sb. use of fem. pp. of miscēre MIX) association of graziers, who appropriated wild cattle.

mus·tang / ˈməsˌtang/ • n. an American feral horse, typically small and lightly built.