Underground may refer to: Underground rapid transit system, urban railway London Underground, a metro system that covers the Greater London area Resistance movement, an opposition to an invader, a political position, or to a government Underground Railroad, a network of secret routes and safe houses used by 19th century black slaves in the U.S. to escape to free states To go underground is to go hiding from the authorities, or from society In film: Underground (1995 film), directed by Em… (More on Underground)