yack away vs talk

yack away is not a noun while talk is a noun.

Word	Noun	Adjective	Verb	Adverb
yack away	No	No	Yes	No
talk	Yes	No	Yes	No

As verbs, talk is a hypernym of yack away; that is, talk is a word with a broader meaning than yack away:

Other hypernyms of yack away include mouth, speak, utter, verbalise, verbalize.

yack away (noun)	talk (noun)
	the act of giving a talk to an audience
	an exchange of ideas via conversation
	idle gossip or rumor
	a speech that is open to the public
	discussion; (`talk about' is a less formal alternative for `discussion of')

yack away (verb)	talk (verb)
talk incessantly and tiresomely	express in speech
	exchange thoughts; talk with
	reveal information
	use language
	deliver a lecture or talk
	divulge confidential information or secrets