'锁死' (suǒ sǐ) is a compound verb meaning 'to lock permanently' or 'to freeze up' — literally 'lock + die'. The character 锁 means 'to lock' or 'to secure', while 死 means 'dead' or 'inactive'; together, they convey the idea of something becoming completely immobilized, unresponsive, or irreversibly fixed in place. It’s commonly used in technical, mechanical, and medical contexts.

In engineering or computing, it describes a system failure where components jam or software becomes unresponsive. In medicine, it often refers to joint immobility — for example, when arthritis causes a knee or shoulder to lose all range of motion. Unlike simple 'locking' (锁定), 锁死 implies severity, irreversibility without intervention, and functional loss. It carries a slightly negative or urgent connotation, signaling that normal operation has ceased entirely.