Simple past tense and past participle of costar.(verb)
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Use "costarred" in a sentence
"(Jane Birkin costarred with Dirk Bogarde in Daddy Nostalgia directed by Bertrand Tavernier.)"
"Â Redgrave made her professional debut in the play A Touch of the Sun (1957), in which she costarred with her father, Sir Michael Redgrave."
"Parnell and Greer have history — they costarred in ABC's underrated gem Miss Guided and both provide voices on FX's animated spy spoof Archer — and they developed a surprisingly potent chemistry in only a few scenes."