Yunbeihaisi
It refers to the melancholy thoughts like clouds and sea.
Idioms and allusions
[from] a comprehensive biography of the king of Yuzhang in the book of Liang Dynasty: "peeping through the mirror, I can't see my face. I feel sad about the clouds and the sea, but I can't think about it."
[example] in Tang Li Bai's feilongyin: "riding a dragon to Taiqing's house is very exciting."
Discrimination of words
[usage] combination; as subject and object; with derogatory meaning
Yunbeihaisi
Honor the past and abuse the present - róng gǔ nüè jīn
attack the enemy at his weak points - pī háng dǎo xū
difficult to guess or comprehend - xuán miào mò cè