nacreous cloud vs mother-of-pearl cloud

nacreous cloud and mother-of-pearl cloud both are nouns.

Word	Noun	Adjective	Verb	Adverb
nacreous cloud	Yes	No	No	No
mother-of-pearl cloud	Yes	No	No	No

As nouns, nacreous cloud and mother-of-pearl cloud are synonyms defined as:

nacreous cloud and mother-of-pearl cloud: a luminous iridescent cloud at a high altitude that may be seen when the sun is a few degrees below the horizon

nacreous cloud (noun)	mother-of-pearl cloud (noun)
a luminous iridescent cloud at a high altitude that may be seen when the sun is a few degrees below the horizon	a luminous iridescent cloud at a high altitude that may be seen when the sun is a few degrees below the horizon