literal meaning: a thousand circles and a hundred turns
translated: full of many twists and turns
千
qiān
thousand
回
huí
return, circle back
百
bǎi
hundred
转
zhuǎn
turn, shift, change
毛不易 - 给你给我
Mao Buyi - Gei Ni Gei Wo
给你我百转千回的喜乐和忧愁
Gěi nǐ wǒ bǎizhuǎn-qiānhuí de xǐlè he yōuchóu
(I'll) give you my ever-changing joy and sorrow
In this lyric, the idiom is used to express how one's emotions keep shifting back and forth between joy and sorrow forever. In the context of the song, the singer tells someone that he will share his joys, sorrows, and everything in between with them during the time they spend together.