overground

Short definition from Wiktionary

Adjective

1. 1
   Above the ground.
2. 2
   Mainstream, not underground.

Noun

1. 1
   A commuter rail or similar rail transport system, or a train in such systems, generally running through an urban area largely above ground and faster than an underground or metro with fewer stops.

Verb

1. 1
   simple past and past participle of overgrind

Proper noun

1. 1
   The London Overground, a counterpart of London Underground operated by TfL (Transport for London), which operates some of the various lines around London which are mainly above ground.