Borrowed from Tibetan གཡག (g.yag). See there for more.
Meanings
An ox-like mammal native to the Himalayas, Mongolia, Myanmar, and Tibet with dark, long, and silky hair, a horse-like tail, and a full, bushy mane.
Attempts are now being made, by selection, to create a new breed of yak (the Datong yak) from such crosses. Hybridization of domestic yak with local cattle, at intermediate elevations, has been practiced for generations. The hybrids inherit some of the good characteristics from each species, but lack the adaptation of the yak to the harsh conditions at higher elevations. 2004, Wilson G. Pond, Encyclopedia of Animal Science (Print), CRC Press, →ISBN, page 899:
Utilization efficiency of dietary protein in the yak differs with diet composition and feeding level, age, sex, body condition score, and animal production level (e.g., growth, lactation). Researchers reported no difference between lactating and dry cows in crude protein digestibility, although lactating yak tend to consume more feed than dry yak. 2008, Scott R. R. Haskell, Blackwell's Five-Minute Veterinary Consult: Ruminant, John Wiley & Sons, →ISBN, page 619:
(countable, slang, uncountable) A talk, particular an informal talk; chattering; gossip.
Sluggsy said indifferently, ‘You’ll be wised up come morning. Meanwhiles, howsabout shuttin’ that dumb little hashtrap of yours? All this yak is bending my ear. I want some action. 1962, Ian Fleming, chapter 9, in The Spy Who Loved Me:
The sudden head-down butt jabbed into someone’s face, is a highly effective way of putting a stop to his yack. 1983, Nicolas Freeling, The Back of the North Wind, →ISBN:
(countable, slang, uncountable) A laugh.
Would-be gags from would-be gagsters. And, nine chances out of ten, not a yak in the lot. 1951, Fredric Brown, Mack Reynolds, Cartoonist:
(intransitive, slang) To talk, particularly informally but persistently; to chatter or prattle.
“You'll like Poppet. Nice dog. Wears his ears inside out. Why do dachshunds wear their ears inside out?” “I could not say, sir.” “Nor me. I've often wondered. But this won't do, Jeeves. Here we are, yakking about Jezebels and dachshunds, when we ought to be concentrating our minds […] 1960, P[elham] G[renville] Wodehouse, chapter XI, in Jeeves in the Offing, London: Herbert Jenkins, →OCLC:
And in the last few days Clair's boundless capacity to yak about herself while Melissa listened had turned Chip against her, too. 2001, Jonathan Franzen, The Corrections:
(intransitive, slang) To vomit, usually as a result of excessive alcohol consumption.
She'll feel better when she yaks. 1998, Tim Herlihy, The Wedding Singer, spoken by Glenn Guglia (Matthew Glave):
Quick cash, flip that, now I got big cash. Sit back, sip yak with a next piff yat. 2018 November 30, “Bits” (track 10), in Original Sounds, performed by Bru-C and Window Kid:
(in-plural, slang) A yakuza member.
These days yaks make most of their money through securities fraud. 2015 September 9, yakthrow, “My neighborhood Yak”, in Reddit, archived from the original on 25 Feb 2026:
Yakuza, or Yaks as they are popularly known, Japan's large and tightly organized crime and illicit drug corporations. 2007, Merrill Singer, Drugging the Poor: Legal and Illegal Drugs and Social Inequality, Waveland Press, →ISBN, page 191:
Don't worry about it, Carter. Yaks aren't gonna be a problem around here? Yaks? Yakuza? 2023, Matthew A. Knorpp, The Killer Who Lost His Mind, Archway Publishing, →ISBN, page 191: