noctilucent cloud


noc·​ti·​lu·​cent cloud ˌnäk-tə-ˈlü-sᵊnt- How to pronounce noctilucent cloud (audio)
: a luminous thin usually colored cloud seen especially at twilight at a height of about 50 miles (80 kilometers)

Example Sentences

Recent Examples on the Web Initially launched on April 25, 2007, the NASA probe orbited about 370 miles above Earth's surface and studied polar mesospheric clouds, which are also known as night-shining or noctilucent clouds. Ariana Garcia, Chron, 21 Mar. 2023 So scientists do not have a long satellite record showing the onset and evolution of the noctilucent cloud season over Antarctica. Tom Yulsman, Discover Magazine, 6 Dec. 2016 The team is the first to demonstrate noctilucent cloud formation is linked to water vapor cooling. Elizabeth Gamillo, Smithsonian Magazine, 10 Mar. 2021 Agencies could educate employees on how to recognize high-altitude balloons hit by moonlight, fireballs that look like floating orbs, noctilucent clouds that resemble extraterrestrial neural networks. Sarah Scoles, Wired, 3 Mar. 2020 But as days get shorter with the onset of fall, noctilucent clouds will fade from view. Andrew Fazekas, National Geographic, 1 Aug. 2019 That water vapor is responsible for the brightening noctilucent clouds, the new study says. Rachel Becker, The Verge, 6 July 2018 Researchers used computer simulations to model the Northern Hemisphere’s atmosphere and noctilucent clouds from 1871 to 2008, according to the study, which was published last week in the journal Geophysical Research Letters. Katie Camero,, 13 July 2018 The first time people reported noticing noctilucent clouds was in 1880s after the massive eruption of Krakatau, a volcano in Indonesia. Rachel Becker, The Verge, 6 July 2018 See More

These examples are programmatically compiled from various online sources to illustrate current usage of the word 'noctilucent cloud.' Any opinions expressed in the examples do not represent those of Merriam-Webster or its editors. Send us feedback about these examples.

Word History


noctilucent "luminous in the dark," from Latin noct-, nox night entry 1 + -i- -i- + lucent

First Known Use

circa 1934, in the meaning defined above

Time Traveler
The first known use of noctilucent cloud was circa 1934

Dictionary Entries Near noctilucent cloud

Cite this Entry

“Noctilucent cloud.” Dictionary, Merriam-Webster, Accessed 7 Jun. 2023.

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