The term subway is a noun which is used to describe an underground urban railroad, typically operated by electricity. It could also refer to a passage meant for such a railroad. A subway may also refer to an underground tunnel or underground passage, such as one for a water main or a subway for pedestrians. In this sense of the term it is used as a synonym for the term underpass.

Simply put it usually refers to an electric underground railway. Others words used to describe a subway include a tube, metro and underground.

Other references to the term Subway include the popular food chain Subway, which is a franchise that specialises in "submarine" sandwiches. There is also a British rock band called the Subways. There is a canyon situated in Zion National Park called Subway. There is also a 1985 film by Luc Besson named Subway.