holler vs let loose

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

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

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

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

holler (noun)	let loose (noun)
a very loud utterance (like the sound of an animal)
a small valley between mountains

holler (verb)	let loose (verb)
complain	express audibly; utter sounds (not necessarily words)
utter a sudden loud cry	turn loose or free from restraint
shout out