yak vs yack

yak and yack both are nouns.

Word	Noun	Adjective	Verb	Adverb
yak	Yes	No	Yes	No
yack	Yes	No	Yes	No

As nouns, yak and yack are synonyms defined as:

Other synonyms of yak include cackle, chatter, yakety-yak.

yak (noun)	yack (noun)
large long-haired wild ox of Tibet often domesticated	noisy talk
noisy talk

yak (verb)	yack (verb)
talk profusely	talk incessantly and tiresomely