sub·ter·ra·nean /ˌsʌbtəˈreniən, njən/
  (a.)地下的,祕密的地下室
  Sub·ter·ra·ne·an Sub·ter·ra·ne·ous a.  Being or lying under the surface of the earth; situated within the earth, or under ground; as, subterranean springs; a subterraneous passage. -- Sub*ter*ra*ne*ous*ly, adv.
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  subterranean
       adj 1: being or operating under the surface of the earth;
              "subterranean passages"; "a subsurface flow of water"
              [syn: subterraneous]
       2: 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
          [syn: subterraneous, ulterior]