待你长发及腰我定满头白发
[dài nĭ zhăng fā jí yāo wŏ dìng măn tóu bái fā]
This translates to 'By the time your hair grows to your waist, I'll surely be full-headed white-haired.' It reflects the longing and the passage of time while waiting for someone, suggesting unfulfilled desire over a long period.