nimbus cloud vs rain cloud

nimbus cloud and rain cloud both are nouns.

Word	Noun	Adjective	Verb	Adverb
nimbus cloud	Yes	No	No	No
rain cloud	Yes	No	No	No

As nouns, nimbus cloud and rain cloud are synonyms defined as:

Other synonyms of nimbus cloud include nimbus.

nimbus cloud (noun)	rain cloud (noun)
a dark grey cloud bearing rain	a dark grey cloud bearing rain