basement or cellar; rooms built below the ground level of a building

water found beneath the earth's surface in soil or rock formations; distinguished from [[地表水|地表水|di4 biao3 shui3]]

an underground political party; specifically used for the Communist Party's secret activities before 1949

A railway system built beneath the ground in a city; underground railway. It is a short form of [[地下铁道|地下鐵道|di4 xia4 tie3 dao4]].

secret or clandestine activities, usually involving political or military groups

A railway system built underground to ease urban traffic; often shortened to [[地铁|地鐵|di4 tie3]] or [[地下铁|地下鐵|di4 xia4 tie3]]

An underground passage, tunnel, or subway for pedestrians or vehicles

A stem of a plant that grows underground, such as a rootstock, tuber, or bulb

underground nuclear explosion; nuclear underground burst

The testing of nuclear weapons by detonating them beneath the surface of the ground

The level below which the ground is saturated with water; underground water level

The upper level of underground water where the soil or rocks are saturated.

An illegal radio station that broadcasts without government approval or registration

the total of all economic activities involving illegal transactions or activities conducted specifically to evade taxes and maximize profits

An illegal or unlicensed dance hall or nightclub

An underground shopping arcade or complex featuring shops and facilities for the public; underground mall

Natural resources found or buried beneath the earth's surface, including minerals, coal, and oil

underground passage; pedestrian underpass

illegal or unlicensed financial institution that operates outside of government regulation; wildcat bank

underground railway; subway

An underground passage for people walking to cross under a road or railway

to go underground; to turn to secret or illegal activities

located or occurring under the surface of the ground; subsurface

A literary expression used as a polite or poetic way to say that a talented scholar or writer has passed away

an honorary term for a scholar or man of letters who has passed away

underground parking lot; basement car park

underground shopping center; basement level of shops

A woman who is a man's secret lover or extramarital partner; synonym for [[情妇|情婦|qing2 fu4]]

an unlicensed or secret factory operating without official approval or legal registration

A romantic relationship or love affair that is kept secret or not publicly disclosed.