- (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
- 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.