noctilucent

American  

[nok-tuh-loo-suhnt] / ˌnɒk təˈlu sənt /

adjective

Meteorology.

1. (of high-altitude clouds) visible during the short night of the summer.

---

noctilucent British  

/ ˌnɒktɪˈluːsənt /

adjective

1. shining at night, usu. of very thin high altitude clouds observable in the summer twilight sky

---

noctilucent Scientific  

/ nŏk′tə-lo̅o̅′sənt /

1. Luminous at night. The term is used especially to describe certain high atmospheric cloud formations visible during summer nights at high latitudes.

---

Other Word Forms

• noctilucence noun

Etymology

Origin of noctilucent

First recorded in 1885–90; nocti- + lucent

Example Sentences

The records contain mentions of major aurora events and some of the first recorded observations of noctilucent clouds which are such a feature of clear summer nights in the north of Ireland.

From BBC • Jul. 13, 2025

“Folks in the northern U.S. and Canada should absolutely be on the lookout for noctilucent clouds over the long weekend,” Cora Randall, a professor at the University of Colorado Boulder, said in an email.

From Washington Post • Jul. 2, 2022

Researchers say these noctilucent, or night-shining, clouds are the rarest, driest and highest clouds on Earth.

From Washington Post • Jul. 2, 2022

It was a close call between John Rowlands' study of noctilucent clouds, and an entry by art gallery owner Shane Record from Kent.

From BBC • Apr. 24, 2010

Like noctilucent clouds high above the cirrus belt.

From The Scarlet Lake Mystery by Goodwin, Harold L. (Harold Leland)