overground

From over- +‎ ground.

overground (not comparable)

1. Above the ground.

   Synonyms: aboveground, superterranean

   Antonym: underground

   an overground railway

   • 2012, Andrew Martin, Underground Overground: A passenger's history of the Tube, Profile Books, →ISBN, page 57:

     We have been concentrating on the City because that was the initial target for builders of both overground and underground railways, who were like artists going over and over the same piece of canvas.

2. Mainstream, not underground.
   • 1974 April 6, “H.C.H.S. Bookstore”, in Gay Community News, page 1:

     They have plans to carry overground books on gay liberation, and a lot of books from small presses.

overground (plural overgrounds)

1. (chiefly London) A commuter rail or similar rail transport system, or a train in such systems, generally running above the ground.

   Coordinate terms: underground, subway

   • 2013, Tobias Hill, The Cryptographer:

     The overground is ten minutes walk through the gloom. Anna finds a seat in the third carriage she tries.

   • 2014, Nicholas Faith, The World the Railways Made:

     Today dozens more systems are being built – or at least being planned with twelve in China alone – and that's not counting the overgrounds and the tramways!

   • 2022 May 19, Lucy Aplin, “New Tube map: How the London Underground map looks with the Elizabeth Line ahead of Crossrail opening”, in i‎:

     TfL has released an official map showing how the new Elizabeth Line will slot in with the existing stations, Tube lines and overgrounds.

• “overground”, in Lexico, Dictionary.com; Oxford University Press, 2019–2022.

overground

1. simple past and past participle of overgrind