shout out vs hollo

shout out is not a noun while hollo is a noun.

Word	Noun	Adjective	Verb	Adverb
shout out	No	No	Yes	No
hollo	Yes	No	Yes	No

As verbs, shout out and hollo are synonyms defined as:

Other synonyms of shout out include call, cry, holler, scream, shout, squall, yell.

As verbs, hollo is a hyponym of shout out; that is, hollo is a word with a more specific, narrower meaning than shout out:

shout out (noun)	hollo (noun)
	a very loud utterance (like the sound of an animal)

shout out (verb)	hollo (verb)
utter a sudden loud cry	utter a sudden loud cry
utter in a very loud voice	cry hollo
	encourage somebody by crying hollo