grunt vs let out

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

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

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

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

grunt (noun)	let out (noun)
medium-sized tropical marine food fishes that utter grunting sounds when caught
the short low gruff noise of the kind made by hogs
an unskilled or low-ranking soldier or other worker

grunt (verb)	let out (verb)
issue a grunting, low, animal-like noise	make (clothes) larger
	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