subway

noun

1. an electric railway operating below the surface of the ground (usually in a city)

   noun.artifact

   Examples

   In Paris the subway system is called the `metro' and in London it is called the `tube' or the `underground'.

   Synonyms metro subway system tube underground

   Source: WordNet 3.0

2. an underground tunnel or passage enabling pedestrians to cross a road or railway

   noun.artifact

   Synonyms underpass

   Source: WordNet 3.0

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

   noun

   Source: webster1913