metro

Etymology 1

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.

noun

1. (general) A rapid transit rail transport system, or a train in such systems, generally underground and serving a metropolitan area.
   Recalling that Davide Lungo returned the van at the airport, Pizo descended the nearby stairs to the underground metro, and boarded the next metro stopping there. 2000, Frederick Parkins, The NATO Opposition, page 27
   I hurry to the underground. ... I am waiting for the next metro; I'll take it. 2014, Lily Sergueiew, I Worked Alone: Diary of a Double Agent in World War II Europe
   What we entered into here was well lit and had clean silver curvy walls that ended in nice automatic elevators that took you underground. The walls are not infested with graffiti and advertisements; they were clean and shiny. We waited on nice benches until the metro arrived. 2017, Pam Taylor, 399 Days: Our European Escapade
2. (less common) An urban rapid transit rail transport system, normally with lighter track and light trains (i.e. an S-Bahn or similar), or a train in such systems.
   Informs how long the passenger has to wait for the next metro 2006, C. A. Brebbia, V. Dolezel, Urban Transport XII: Urban Transport and the Environment in the 21st Century, page 227
   With the weather clear and warm for a change, I decided to catch the next metro to the outskirts of town by myself. 2008, Brandon Wilson, Along the Templar Trail: Seven Million Steps for Peace, page 75
   I boarded the Yellow Line Metro, beaming with confidence. I got down at Rajiv Chowk to continue my journey towards Noida City Centre (NCC). The next metro arrived. 2015, Pratyush Sinha, Love in Metro: Story of Love and Ego

Etymology 2

Clipping of metropolitan.

noun

1. A metropolitan area.
   In an age of persistently high inequality, work in high-cost metros catering to the whims of the wealthy—grooming them, stretching them, feeding them, driving them—has become one of the fastest-growing industries. 2019-08-12, Derek Thompson, “America's Hot New Job Is Being a Rich Person's Servant”, in The Atlantic

adj

1. metropolitan