卧薪尝胆 (臥薪嘗膽) wò xīn cháng dǎn

wò xīn cháng dǎn set phrase lie on firewood and taste gall; to harden oneself for revenge
Domain: Idiom 成语
Notes: (CC-CEDICT '卧薪尝胆'; CCI p. 31; Guoyu '臥薪嘗膽')