holloa vs roar

holloa and roar both are nouns.

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

As nouns, holloa and roar are synonyms defined as:

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

holloa (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

holloa (verb)	roar (verb)
	laugh unrestrainedly and heartily
	make a loud noise, as of wind, water, or vehicles
	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