A dragstrip, a place where drag races are held. A racetrack to drag on.
An underground route for pipes, sewers, etc.
A rapid transit system, regardless of the elevation of its right of way; a metro system.
An underground railway, especially for mass transit of people in urban areas.
A train that runs on such an underground railway.
An underground walkway, tunnel for pedestrians (called pedestrian underpass in US).
To travel by underground railway.