yak (1)EnglishOxford New American Dictionaryyak1 /yak, jæk / ▸ noun (plural same or yaks) a large domesticated wild ox with shaggy hair, humped shoulders, and large horns, used in Tibet as a pack animal and for its milk, meat, and hide. Genus Bos, family Bovidae; the domesticated B. grunniens, descended from the wild B. mutus, which rarely is still found at high altitude. – ORIGIN late 18th century : from Tibetan gyag.