roar vs ululate

roar is a noun but ululate is not a noun.

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

As verbs, roar and ululate are synonyms defined as:

Other synonyms of roar include howl, wail, yaup, yawl.

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

roar (verb)	ululate (verb)
laugh unrestrainedly and heartily	emit long loud cries
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