Tra từ Underground - Từ điển Oxford Advanced Learner 8th

under·ground [underground] adjective, adverb, noun
adjective BrE [ˌʌndəˈɡraʊnd] ; NAmE [ˌʌndəˈɡraʊnd] only before noun
1. under the surface of the ground
•underground passages/caves/streams
•underground cables
compare ↑overground
2. operating secretly and often illegally, especially against a government
•an underground resistance movement

Example Bank:
•The changes will affect all workers, whether underground or legal.
•The party was originally formed as an underground organization in 1987.

adverb BrE [ˌʌndəˈɡraʊnd] ; NAmE [ˌʌndərˈɡraʊnd]
1. under the surface of the ground
• Rescuers found victims trapped several feet underground.
•toxic waste buried deep underground
•a network of pipelines running underground
2. in or into a secret place in order to hide from the police, the government, etc
• He went underground to avoid arrest.

Example Bank:
•If the group is outlawed they will go underground.

noun

BrE [ˈʌndəɡraʊnd] ; NAmE [ˈʌndərɡraʊnd]
1. (often the Underground) (BrE) (NAmE sub·way)singular an underground railway/railroad system in a city
•underground stations
•the London Underground
•I always travel by underground.
compare ↑metro, ↑tube
2. the undergroundsingular + singular or plural verb a secret political organization, usually working against the government of a country

British/American:
underground / subway / metro / tube
A city’s underground railway/railroad system is usually called the underground (often the Underground) in BrE and the subway in NAmE. Speakers of BrE also use subway for systems in American cities and metro for systems in other European countries. The Metro is the name for the systems in Paris and Washington, D.C. London’s system is often called the Tube.

Example Bank:
•I always seem to get lost in the underground.
•I often travel on the underground.
•It brought the whole underground system to a halt.
•We went by underground.

See also: ↑subway