splutter vs let loose

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

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

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

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

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

splutter (verb)	let loose (verb)
spit up in an explosive manner	express audibly; utter sounds (not necessarily words)
utter with a spitting sound, as if in a rage	turn loose or free from restraint