yak, n.¹ — Green’s Dictionary of Slang

yak n.¹

[yack v. (1); i.e. one who talks rubbish all the time; and/or someone who looks like a SE yak]

(US) a general term of abuse.

1995		(con. 1985–90) P. Bourjois In Search of Respect 23: The fat yak is on the rag. He’ll get over it.
1997–2001		Online Sl. Dict. 🌐 yak n 1. an unattractive female, usually due to morbid obesity or bovine-like odor.