yammer vs let out

yammer and let out both are verbs.

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

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

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

yammer (verb)	let out (verb)
complain whiningly	make (clothes) larger
cry loudly, as of animals	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