n.
Pronunciation: ' ə n-d ə r- ˌ grau ̇ nd
Function: adjective
Date: 1601
1 : being, growing, operating, or situated below the surface of the ground
2 : conducted by secret means
3 a : existing outside the establishment <an underground literary reputation> b : existing outside the purview of tax collectors or statisticians <the underground economy>
4 a : produced or published outside the establishment especially by the avant-garde < underground movies> < underground newspapers> b : of or relating to the avant-garde underground <an underground moviemaker> <an underground theater>