The Collaborative International Dictionary
Yak \Yak\ (y[a^]k), n. [Tibetan gyag.] (Zo["o]l.) A bovine mammal ( Po["e]phagus grunnies) native of the high plains of Central Asia. Its neck, the outer side of its legs, and its flanks, are covered with long, flowing, fine hair. Its tail is long and bushy, often white, and is valued as an ornament and for other purposes in India and China. There are several domesticated varieties, some of which lack the mane and the long hair on the flanks. Called also chauri gua, grunting cow, grunting ox, sarlac, sarlik, and sarluc.
Yak lace, a coarse pillow lace made from the silky hair of the yak.
Wiktionary
n. A coarse pillow lace made from the silky hair of the yak.
Wikipedia
Yak lace refers to a coarse bobbin lace typically made from wool. It was mainly made in Oxfordshire, Buckinghamshire and Northamptonshire in imitation of Maltese and Greek laces. While the name suggests the lace is made using yak hair, it can be made of any wool or worsted yarn.
Whilst woolen laces had been made from the 17th century onwards, it was not until the mid 19th century that "yak lace" became popular. Despite the difficulty of working with naturally elastic woolen yarn which meant that the lace instantly shrank to two thirds of its size once unpinned from the pillow, it was inexpensive, quick and easy to make and became popular and widely used. Yak lace could be produced in various weights, ranging from lightweight trimmings for children's dresses and underwear, to heavier, upholstery-weight lace suitable for curtains. Black yak lace was also widely used for mourning dress. The popularity of woolen lace was boosted by the nineteenth century hygienist Gustav Jäger's promotion of wool fabrics.