rabbit on vs utter

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

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

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

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

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

rabbit on (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