subway

An underground urban railroad, usually operated by electricity.

A passage for such a railroad.

An underground tunnel or passage, as for a water main or for pedestrians.

An underground way; an accessible underground passage containing gas- and water-mains, telegraph-wires, etc.

An underground way or gallery; especially, a passage under a street, in which water mains, gas mains, telegraph wires, etc., are conducted.

An underground railroad, usually having trains powered by electricity provided by an electric line running through the underground tunnel. It is usually confined to the center portion of cities; — called also tube, and in Britain, underground. In certain other countries (as in France or Russia) it is called the metro.

An underground railway, especially for mass transit of people in urban areas.

A rapid transit system, regardless of the elevation of its right of way.

underground walkway, tunnel for pedestrians (called pedestrian underpass in US).