rattle on vs utter

rattle on is not an adjective while utter is an adjective.

Word	Noun	Adjective	Verb	Adverb
rattle on	No	No	Yes	No
utter	No	Yes	Yes	No

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

Other hypernyms of rattle on include mouth, speak, talk, verbalise, verbalize.

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

rattle on (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