‘坑道’ literally combines ‘坑’ (kēng), meaning ‘pit’ or ‘excavation’, and ‘道’ (dào), meaning ‘path’ or ‘way’. Together, it refers to a man-made underground passage—typically narrow, dug into earth or rock—used for military defense, mining, infrastructure, or shelter. Unlike the more general term ‘隧道’ (suìdào), which often implies engineered, lined, and accessible transport tunnels, ‘坑道’ emphasizes manual excavation and functional simplicity; it evokes wartime bunkers, mine shafts, or emergency shelters.

The word carries a slightly technical or historical tone and appears frequently in contexts involving engineering, military history, geology, or civil defense. It is rarely used for modern subway systems or road tunnels. In everyday speech, native speakers may use it specifically when referring to wartime relics (e.g., WWII or Cold War-era fortifications) or underground mining works—not for ordinary underground walkways or basements.