Meaning of open cluster

o'pen clus'ter

Pronunciation: [key]
— Astron. Astron.
  1. a comparatively young, irregularly shaped group of stars, often numbering up to several hundred, and held together by mutual gravitation; usually found along the central plane of the Milky Way and other galaxies.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.