1un·der·ground 
/ˈʌndɚˌgraʊnd/ adjective
/ˈʌndɚˌgraʊnd/ adjective 1 : located or occurring below the surface of the earth
▪ underground parking garages ▪ an underground explosion — compare aboveground, inground 2 always used before a noun : secret and usually illegal
▪ an underground deal ▪ The drugs are supplied through an underground network. 3 always used before a noun : of, relating to, or produced in a social and artistic world that is different and separate from the main part of society
▪ She loves the city's underground music scene. ▪ underground newspapers/movies
▪ underground parking garages ▪ an underground explosion — compare aboveground, inground
▪ an underground deal ▪ The drugs are supplied through an underground network.
▪ She loves the city's underground music scene. ▪ underground newspapers/movies
