垂死 (chuí sǐ) literally combines 垂 (chuí), meaning 'to hang down' or 'to be on the verge of', and 死 (sǐ), meaning 'death'. Together, they form a literary and formal adjective meaning 'on the verge of death' — describing someone or something in an extremely critical, near-fatal condition. It emphasizes imminent, irreversible collapse, often with strong emotional or dramatic weight.

This term is rarely used in casual speech; it appears mainly in written narratives, medical reports, news headlines, or solemn descriptions of life-threatening situations. While it can technically describe animals or plants, its most frequent context is human health crises — such as severe illness, trauma, or terminal decline. The phrase carries gravity and urgency, implying little to no hope of recovery without immediate intervention.