(of high-altitude clouds) visible during the short night of the summer.
Origin of noctilucent
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019
shining at night, usu. of very thin high altitude clouds observable in the summer twilight sky
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012
Luminous at night. The term is used especially to describe certain high atmospheric cloud formations visible during summer nights at high latitudes.
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