nacreous cloud
/ˈneɪkrɪəs ˌklaʊd/noun
An iridescent cloud; (specifically in Meteorology ) one of a kind occasionally seen in winter in high latitudes, showing bright colours after sunset, and forming in the stratosphere at a height of 12–18 miles (20–30 kilometres); also called mother-of-pearl cloud.
Origin
Early 20th century. From nacreous + cloud.