roar vs waul

roar is a noun but waul is not a noun.

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

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

Other hyponyms of roar include squall, wawl.

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

roar (verb)	waul (verb)
laugh unrestrainedly and heartily	make high-pitched, whiney noises
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