thunder vs roar

thunder and roar both are nouns.

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

As nouns, thunder and roar are synonyms defined as:

Other synonyms of thunder include boom, roaring.

As verbs, thunder and roar are synonyms defined as:

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

Other hypernyms of thunder include howl.

thunder (noun)	roar (noun)
street names for heroin	a very loud utterance (like the sound of an animal)
a deep prolonged loud noise	a deep prolonged loud noise
a booming or crashing noise caused by air expanding along the path of a bolt of lightning	the sound made by a lion

thunder (verb)	roar (verb)
utter words loudly and forcefully	laugh unrestrainedly and heartily
to make or produce a loud noise	make a loud noise, as of wind, water, or vehicles
move fast, noisily, and heavily	emit long loud cries
be the case that thunder is being heard	utter words loudly and forcefully
	make a loud noise, as of animal
	act or proceed in a riotous, turbulent, or disorderly way