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Messier number

American  

noun

Astronomy.

  1. a number (preceded by M) designating the 109 double stars, clusters, nebulae, and galaxies in the Messier catalog.

Definitions and idiom definitions from Dictionary.com Unabridged, based on the Random House Unabridged Dictionary, © Random House, Inc. 2023

Idioms from The American Heritage® Idioms Dictionary copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.