jabber vs utter

jabber is a noun but utter is not a noun.

Word	Noun	Adjective	Verb	Adverb
jabber	Yes	No	Yes	No
utter	No	Yes	Yes	No

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

Other hypernyms of jabber include mouth, speak, talk, verbalise, verbalize.

jabber (noun)	utter (noun)
rapid and indistinct speech

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

jabber (verb)	utter (verb)
talk in a noisy, excited, or declamatory manner	express in speech
	articulate; either verbally or with a cry, shout, or noise
	express audibly; utter sounds (not necessarily words)
	put into circulation