Wiktionary
n. (context UK English) A county-level administrative division that covers a large urban area
Wikipedia
The metropolitan counties are a type of county-level administrative division of England. There are six metropolitan counties, which each cover large urban areas, typically with populations of 1.2 to 2.8 million. They were created in 1972 and are each divided into several metropolitan districts or boroughs.
The metropolitan county councils were abolished in 1986 with most of their functions being devolved to the individual boroughs, making them de facto unitary authorities. The remaining functions were taken over by joint boards.
The metropolitan counties have population densities of between 800 ( South Yorkshire) and 2,800 ( West Midlands) people/km². Individual metropolitan districts range from 4,000 people/km² in Liverpool to only 500 people/km² in Doncaster. Today, residents of metropolitan counties account for around 22% of the population of England, or 18% of the United Kingdom.