Underground Railway
— Noun
– English
～ secret aid to escaping slaves that was provided by abolitionists in the years before the American Civil War
underground
— Noun
– English
～ an electric railway operating below the surface of the ground (usually in a city); "in Paris the subway system is called the `metro' and in London it is called the `tube' or the `underground'"
underground press
— Noun
– English
～ a system of clandestine printing and distribution of dissident or banned literature
underground
— Noun
– English
～ a secret group organized to overthrow a government or occupation force
Underground Railroad
— Noun
– English
～ secret aid to escaping slaves that was provided by abolitionists in the years before the American Civil War