waul vs roar

waul is not a noun while roar is a noun.

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

As verbs, roar is a hypernym of waul; that is, roar is a word with a broader meaning than waul:

Other hypernyms of waul include howl, ululate, wail, yaup, yawl.

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

waul (verb)	roar (verb)
make high-pitched, whiney noises	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