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Meaning of costar

co•star

Pronunciation: (n.kō'stär"v.kō'stär'), [key]
— n., v., -starred, -star•ring.
—n.
  1. a performer, esp. an actor or actress, who shares star billing with another.
  2. a performer whose status is slightly below that of a star.
—v.i.
  1. to share star billing with another performer.
  2. to receive billing of slightly less status than that of a star.
—v.t.
  1. to present (two or more actors) as having equal billing or prominence.
  2. to present as having slightly less status than that of a star.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.