howl vs squeal

howl and squeal both are nouns.

Word	Noun	Adjective	Verb	Adverb
howl	Yes	No	Yes	No
squeal	Yes	No	Yes	No

As nouns, squeal is a hyponym of howl; that is, squeal is a word with a more specific, narrower meaning than howl:

howl (noun)	squeal (noun)
a long loud emotional utterance	a high-pitched howl
a loud sustained noise resembling the cry of a hound
the long plaintive cry of a hound or a wolf

howl (verb)	squeal (verb)
laugh unrestrainedly and heartily	confess to a punishable or reprehensible deed, usually under pressure
make a loud noise, as of wind, water, or vehicles	utter a high-pitched cry, characteristic of pigs
emit long loud cries
cry loudly, as of animals