沉鱼落雁之貌闭月羞花之容
[chén yú luò yàn zhī mào bì yuè xiū huā zhī róng]
A very descriptive phrase meaning 'a face that makes fish sink and geese alight and a countenance that outshines the moon and makes flowers blush.' Traditionally, it refers to stunning, unparalleled beauty, likely used humorously rather than seriously.