bark vs let loose

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

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

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

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

bark (noun)	let loose (noun)
a sailing ship with 3 (or more) masts
the sound made by a dog
a noise resembling the bark of a dog
tough protective covering of the woody stems and roots of trees and other woody plants

bark (verb)	let loose (verb)
tan (a skin) with bark tannins	express audibly; utter sounds (not necessarily words)
make barking sounds	turn loose or free from restraint
speak in an unfriendly tone
remove the bark of a tree
cover with bark