splutter vs let out

splutter is a noun but let out is not a noun.

Word	Noun	Adjective	Verb	Adverb
splutter	Yes	No	Yes	No
let out	No	No	Yes	No

As verbs, let out is a hypernym of splutter; that is, let out is a word with a broader meaning than splutter:

Other hypernyms of splutter include emit, let loose, utter.

splutter (noun)	let out (noun)
an utterance (of words) with spitting sounds (as in rage)
the noise of something spattering or sputtering explosively

splutter (verb)	let out (verb)
spit up in an explosive manner	make (clothes) larger
utter with a spitting sound, as if in a rage	make known to the public information that was previously known only to a few people or that was meant to be kept a secret
	express audibly; utter sounds (not necessarily words)
	bring out of a specific state