Underground: meaning, definitions and examples

Used primarily in British English to refer to a city's public transportation system that operates below ground level.

• The London Underground is one of the oldest metro systems in the world.
• She takes the underground to work every morning.

Primarily used in American English for underground urban train systems.

• The New York City subway operates 24/7.
• I'm taking the subway to the concert tonight.

Commonly used in European and some international cities to describe an urban rapid transit system.

• The Paris Metro is known for its extensive network.
• They are expanding the metro service to reach more suburbs.

Colloquial term used in London to refer to their underground rail system.

• You can get to Covent Garden directly on the Piccadilly line of the tube.
• He's been riding the tube for years and knows all the shortcuts.

Used to describe something that exists below the surface or out of the public eye, often in a physical sense or to describe a movement that is not mainstream.

• The subway system is an extensive underground network
• The band's music was part of the underground scene in the '90s

Typically used for activities that are intentionally concealed, usually implying a level of secrecy and often connected to military or surveillance activities.

• The agency carried out a covert mission to gather intelligence
• Their covert actions were crucial in disrupting the plot

Used to describe secretive or concealed activities, often illegal or done to avoid detection.

• They held clandestine meetings to plan the revolution
• The spy was part of a clandestine operation

Describes something that is not visible or easily found, generally in a straightforward physical or metaphorical sense.

• The key was hidden under the doormat
• She kept her true feelings hidden from everyone