subway

sub‧way /ˈsʌbweɪ/ BrE AmE noun [countable]
[Word Family: noun: ↑way, ↑subway; adverb: ↑midway, ↑way; adjective: ↑midway]
1. American English a railway system that runs under the ground below a big city SYN underground British English:
the New York City subway
a crowded subway station
Boston has the oldest subway system in the US.
2. British English a path for people to walk under a road or railway SYN underpass
• • •
THESAURUS
▪ the subway American English the railway system that runs under the ground below a big city. British people use the underground when talking about the railway system in London, and many systems outside the US: the New York subway | We got on the next subway train.
▪ the underground British English the railway system that runs under the ground below a big city: the London underground | an underground map | It’s quickest to travel by underground.
▪ the tube British English informal the railway system that runs under London: We took the tube to Trafalgar Square. | a crowded tube train
▪ the metro used especially to talk about the railway system that runs under Paris. Also used about some other city's systems, for example Moscow, Washington DC and Newcastle: the Paris Metro | Moscow’s metro stations

Oxford Advanced Learner's Dictionary

subway

sub·way [subway subways] [ˈsʌbweɪ] [ˈsʌbweɪ] noun

1. (NAmE) an underground railway/railroad system in a city
• the New York subway
• a subway station/train
• a downtown subway stop
• to ride/take the subway

• In Boston the subway is known as the ‘T’; in Washington DC it's the‘Metro’.

2. (BrE) a path that goes under a road, etc. which people can use to cross to the other side
Syn: underpass
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:
• He ran through the pedestrian subway.
• I've never been on the subway.
• Yankee Stadium is a 40-minute subway ride from our house.

• rush hour in the subway

Cambridge Advanced Learner's Dictionary

subway

subway (UNDERGROUND RAILWAY) /ˈsʌb.weɪ/
noun [C] MAINLY US
a railway system in which electric trains travel along passages below ground:
We took the subway uptown to Yankee Stadium.

subway (UNDERGROUND PASSAGE) /ˈsʌb.weɪ/
noun [C] UK
an underground passage which allows people on foot to cross a busy road

underpass

underpass /ˈʌn.də.pɑːs/ US /-dɚ.pæs/
noun [C] (UK subway)
a road or path that goes under something such as a busy road, allowing vehicles or people to go from one side to the other

Collins COBUILD Advanced Learner’s English Dictionary

subway

/sʌbweɪ/
(subways)

1.
A subway is an underground railway. (mainly AM; in BRIT, use underground, tube)
...the Bay Area Rapid Transit subway system...
I don’t ride the subway late at night.
N-COUNT: oft N n, also by N

2.
A subway is a passage underneath a busy road or a railway track for people to walk through. (BRIT; in AM, use underpass)
N-COUNT

Merriam-Webster's Advanced Learner's Dictionary

Merriam-Webster's Advanced Learner's Dictionary:

subway

sub·way /ˈsʌbˌweɪ/ noun, pl -ways [count]
1 chiefly US : a system of underground trains in a city
• I took/rode the subway to midtown.
• No one on the subway seemed to mind how crowded it was.
• I've been on both the New York subway and the Underground in London.
- often used before another noun
• a subway car/station
• the subway platform
2 Brit : a road or passage for walking under a road, set of railroad tracks, etc. : underpass