verb

• (slang, intransitive) 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 […]"
• (slang, intransitive) To vomit, usually as a result of excessive alcohol consumption.
  "She'll feel better when she yaks."

noun

• (slang) 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."
• (slang) A laugh.
  "Would-be gags from would-be gagsters. And, nine chances out of ten, not a yak in the lot."
• (slang) Vomit.

noun

• (slang) A kayak.

noun

• (slang) cognac.
  "Quick cash, flip that, now I got big cash. Sit back, sip yak with a next piff yat."