n. 预备演员, 替角
vt. 通过观察掌握某工作, 通过实习掌握某工作
vt.vi. 练习当替角
在线英汉词典

understudy的短语、例句：

understudy n ~ (to sb) person who learns the part of another in a play, etc in order to be able to take his place at short notice if necessary 候补演员; 替手
(fig 比喻) The Vice-President acts as understudy to the President. 副总统是总统的替手. understudy, v (pt, pp -died) [Tn] learn (eg a part in a play) as understudy; act as understudy to (sb) 排练（如剧中角色）充当候补演员; 当（某人）的替手
understudy (the role of) Ophelia 排练奥菲利亚（一角）当候补演员
She understudied Judi Dench. 她充当朱迪.登奇的替手.