metro
n. countablen. an underground train system in a city. You use it to travel quickly around large urban areas.
n. an underground electric railway system in a major city. Often used with a definite article when referring to a specific city's network.
I take the metro to work every morning.
The city is expanding the metro to reach the outer suburbs and reduce traffic congestion.
Navigating the Parisian metro requires a basic understanding of the line numbers and the final destinations of each route to ensure you board the correct train.
From French métro, clipping of métropolitain (from Ancient Greek μήτηρ (mḗtēr, “mother”) + πόλις (pólis, “city”)), as in the Chemin de fer métropolitain, an early name for the Paris Métro. This name was a direct translation of "Metropolitan Railway", which was the original name of the earliest part of the London Underground, constructed in 1863.
Clipping of metropolitan.
Often used with 'the' when referring to a specific city's system.