meow vs let out

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

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

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

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

meow (noun)	let out (noun)
the sound made by a cat (or any sound resembling this)

meow (verb)	let out (verb)
cry like a cat	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