- (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. 2018
- 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.
The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.