stammer vs utter

stammer is a noun but utter is not a noun.

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

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

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

stammer (noun)	utter (noun)
a speech disorder involving hesitations and involuntary repetitions of certain sounds

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

stammer (verb)	utter (verb)
speak haltingly	express in speech
	articulate; either verbally or with a cry, shout, or noise
	express audibly; utter sounds (not necessarily words)
	put into circulation