Definition: Having a pearly appearance
Synonyms: opalescent, iridescent, pearly
Originating in 1590s Middle French, this adjective derives from the word nacre which is a type of a shellfish that yields mother of pearl.
Why this word?
Although generally used with phenomenon pertaining to cloud formation, this picturesque word has a few more possible uses.
Nacreous clouds, or simply Nacreous, are most beautiful of all cloud formations, yet they are also the most destructive to our atmosphere. Their presence encourages chemical reactions breaking down the ozone layer, which acts as an essential shield protecting us from the most harmful of the sun’s rays. Nacreous clouds are generally observed at heights of 20 to 30 kilometers above sea level.
As promised, here is one more place where you observe that analogous pearly luster; that is when petrol is dropped on the road during a rainy day, a thin layer of oil will appear on the water surface. As a result, a rainbow-like color pattern is shown on the oily surface. The causal phenomenon in both cases is the same and has to do with thin film interference- one is transpiring on the earth and the other in welkin.
How to use the word nacreous in a sentence?
Nacreous clouds exhibit spectacular iridescent pastel colors, caused by the sunlight diffracting as it passes around their tiny ice crystals.
“At other times he would take the things he had made, and winding them on strings, hang garlands before her, and burn perfumes, chanting strangely, while the fumes wreathed and blotted the shadow face, as with cloudy, nacreous lace. (“Sword Blades and Poppy Seed”, Amy Lowell)