n. 1. An underground way or gallery; especially, a passage under a street, in which water mains, gas mains, telegraph wires, etc., are conducted. [ 1913 Webster ]
2. An underground railroad, usually having trains powered by electricity provided by an electric line running through the underground tunnel. It is usually confined to the center portion of cities; -- called also tube, and in Britain, underground. In certain other countries (as in France or Russia) it is called the metro. [ PJC ]
(n) an electric railway operating below the surface of the ground (usually in a city), Syn. tube, underground, subway system, subway, Example:in Paris the subway system is called the `metro' and in London it is called the `tube' or the `underground'
[西直门 / 西直門, Xī zhí ménㄒㄧ ㄓˊ ㄇㄣˊ] Xizhimen neighborhood of Beijing; Xizhimen, the main Beijing gate leading northwest; now a subway station on the way to Beijing and Tsinghua Universities#36750
[奥姆真理教 / 奧姆真理教, ào mǔ zhēn lǐ jiàoㄠˋ ㄇㄨˇ ㄓㄣ ㄌㄧˇ ㄐㄧㄠˋ] Aum Shinrikyo, the Japanese death cult responsible for the 1995 sarin gas attack on the Tokyo subway#85688