hollo vs roar

hollo and roar both are nouns.

Word	Noun	Adjective	Verb	Adverb
hollo	Yes	No	Yes	No
roar	Yes	No	Yes	No

As nouns, hollo and roar are synonyms defined as:

Other synonyms of hollo include bellow, bellowing, holla, holler, hollering, holloa, roaring, yowl.

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

hollo (noun)	roar (noun)
a very loud utterance (like the sound of an animal)	a very loud utterance (like the sound of an animal)
	a deep prolonged loud noise
	the sound made by a lion

hollo (verb)	roar (verb)
utter a sudden loud cry	laugh unrestrainedly and heartily
cry hollo	make a loud noise, as of wind, water, or vehicles
encourage somebody by crying hollo	emit long loud cries
	utter words loudly and forcefully
	make a loud noise, as of animal
	act or proceed in a riotous, turbulent, or disorderly way