costar

American  

[koh-stahr, koh-stahr] / ˈkoʊˌstɑr, ˈkoʊˈstɑr /

Or co-star

noun

1. a performer, especially an actor or actress, who shares star billing with another.

2. a performer whose status is slightly below that of a star.

---

verb (used without object)

costarred, costarring

1. to share star billing with another performer.

2. to receive billing of slightly less status than that of a star.

verb (used with object)

costarred, costarring

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.

Etymology

Origin of costar

An Americanism dating back to 1915–20; co- + star

Example Sentences

Instead, she at first finds Mr. Hamm’s “Mad Men” costar, a touchy John Slattery, living out of his garage.

From The Wall Street Journal • Jan. 29, 2026

In real life, Bardot left Vadim for her costar Jean-Louis Trintignant.

From Los Angeles Times • Dec. 28, 2025

“Well, it’s Ken Watanabe; he has that aura, that presence that was overwhelming,” star Kento Yamazaki told Salon about his costar in the pivotal scene.

From Salon • Sep. 29, 2025

Mirren and Brosnan are not the first to push back on the idea of Bond being played by a woman, with the sentiment echoed by Brosnan's Die Another Day costar, Halle Berry.

From BBC • Aug. 17, 2025

Second, the reconciliation and ensuing correspondence permitted Adams to join Jefferson as the costar of an artfully arranged final act in the revolutionary drama.

From "Founding Brothers: The Revolutionary Generation" by Joseph J. Ellis