yowl vs hollo

yowl and hollo both are nouns.

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

As nouns, yowl and hollo are synonyms defined as:

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

yowl (noun)	hollo (noun)
a very loud utterance (like the sound of an animal)	a very loud utterance (like the sound of an animal)

yowl (verb)	hollo (verb)
utter shrieks, as of cats	utter a sudden loud cry
cry loudly, as of animals	cry hollo
	encourage somebody by crying hollo