mother-of-pearl cloud vs nacreous cloud

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

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

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

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

mother-of-pearl cloud (noun)	nacreous 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