scream vs let out

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

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

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

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

scream (noun)	let out (noun)
sharp piercing cry
a joke that seems extremely funny
a high-pitched noise resembling a human cry

scream (verb)	let out (verb)
utter a sudden loud cry	make (clothes) larger
utter or declare in a very loud voice	make known to the public information that was previously known only to a few people or that was meant to be kept a secret
make a loud, piercing sound	express audibly; utter sounds (not necessarily words)
	bring out of a specific state