Dictionary
o'pen clus'ter
Astron.
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.
Also,galactic cluster.Cf.
globular cluster, stellar association. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.