'终身遗憾' literally means 'lifetime regret' — a deep, enduring sorrow or remorse that lasts one's entire life. The compound combines 终身 (zhōngshēn), meaning 'lifelong' or 'for one's whole life', and 遗憾 (yíhàn), meaning 'regret' or 'a feeling of disappointment over something unfulfilled or lost. Together, they convey a profound, irreversible sense of loss — often tied to missed opportunities, broken relationships, or unachieved dreams.

This phrase is typically used in serious, reflective contexts: eulogies, personal reflections, literature, or heartfelt conversations. It carries emotional weight and gravity — not for minor disappointments, but for pivotal, life-defining moments one cannot undo. It’s common in both spoken and written Chinese, especially when expressing sincere, mature regret with lasting consequences.