Yak, large, long-haired ox, native to Tibet, with domesticated varieties throughout Central Asia; it inhabits barren heights up to 6, 100m. Domesticated varieties are smaller and varied in colour; they breed freely with domestic cattle. Wild yaks have coarse black hair, except on the tail and flanks, where it hangs as a long fringe. The horns curve outwards. Height: to 1.8m at the shoulder. Family Bovidae; species Bos mutus.