Main Entry: sub·ter·ra·nean

Pronunciation: \ˌsəb-tə-ˈrā-nē-ən, -nyən\

Variant(s): also sub·ter·ra·neous \-nē-əs, -nyəs\

Function: adjective

Etymology: Latin subterraneus, from sub- + terra earth — more at thirst

Date: 1603

1 : being, lying, or operating under the surface of the earth
2 : existing or working in secret : hidden <a subterranean network of criminals>

— sub·ter·ra·nean·ly also sub·ter·ra·neous·ly adverb