rain vs cloudburst

rain and cloudburst both are nouns.

Word	Noun	Adjective	Verb	Adverb
rain	Yes	No	Yes	No
cloudburst	Yes	No	No	No

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

rain (noun)	cloudburst (noun)
anything happening rapidly or in quick successive	a heavy rain
water falling in drops from vapor condensed in the atmosphere
drops of fresh water that fall as precipitation from clouds

rain (verb)	cloudburst (verb)
precipitate as rain