紧闭 (jǐn bì) is an adjective meaning 'tightly shut' — describing something closed so firmly that no gap remains, often implying effort, intention, or physical force. The first character 紧 (jǐn) means 'tight', 'tense', or 'close', while 闭 (bì) means 'to close' or 'to shut'. Together, they emphasize the completeness and firmness of closure, not just a passive state but an actively secured one.

This term is commonly used for doors, windows, eyes, lips, or even abstract concepts like 'mouth' in expressions like '紧闭嘴巴' (keep one's mouth tightly shut). It appears frequently in descriptive writing, instructions ('紧闭门窗' — seal doors and windows), safety warnings, and literary contexts to convey tension, secrecy, or protection. Unlike simple 闭, which can be neutral or temporary, 紧闭 carries a stronger sense of finality, intensity, or urgency.