Meaning of subterranean

Definition of subterranean

(adj) being or operating under the surface of the earth; "subterranean passages"; "a subsurface flow of water"
lying beyond what is openly revealed or avowed (especially being kept in the background or deliberately concealed); "subterranean motives for murder"; "looked too closely for an ulterior purpose in all knowledge"- Bertrand Russell

Other information on subterranean

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