Synonyms: metro, tube, underground, subway, subway system
Definition: an electric railway operating below the surface of the ground (usually in a city)
Usage: in Paris the subway system is called the `metro' and in London it is called the `tube' or the `underground'
Similar words: railroad, railroad line, railway, railway line, railway system
Definition: line that is the commercial organization responsible for operating a system of transportation for trains that pull passengers or freight
Definition: an underground tunnel or passage enabling pedestrians to cross a road or railway
Similar words: tunnel
Definition: a passageway through or under something, usually underground (especially one for trains or cars)
Usage: the tunnel reduced congestion at that intersection