🇺🇸 [ˌʌndərˈɡraʊnd]
Located below the surface of the earth, especially in reference to structures or passages. It can refer to subterranean areas such as tunnels, subways, or underground bunkers. Additionally, it can be used to describe things that are unconventional or outside the mainstream.
subterranean • below ground • hidden
above ground • overhead • surface