yap away vs utter

yap away is not an adjective while utter is an adjective.

Word	Noun	Adjective	Verb	Adverb
yap away	No	No	Yes	No
utter	No	Yes	Yes	No

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

Other hypernyms of yap away include mouth, speak, talk, verbalise, verbalize.

yap away (adjective)	utter (adjective)
	complete and absolute
	without qualification; used informally as (often pejorative) intensifiers

yap away (verb)	utter (verb)
talk incessantly and tiresomely	express in speech
	articulate; either verbally or with a cry, shout, or noise
	express audibly; utter sounds (not necessarily words)
	put into circulation