understudy

['ʌndəstʌdɪ]

释义

n.候补演员；替身
a performer who learns the role of another in order to serve as a replacement if necessary.

例句
Woman: Hi, oh, I'm Lauren, Kate's understudy.I'm a big fan of yours.(Friends)
女人：嗨，我是劳伦，凯特的替补演员。我是你的超级粉丝。（老友记）