underground
CEFR: A2
Situated, operating, or constructed beneath the surface of the earth; or a subterranean railway transport system.
Synonyms
- subterranean
- subsurface
- metro
Common Collocations
- underground railway
- underground water
- underground network
Example Sentence
The London Underground, inaugurated in eighteen sixty-three, was the world’s first subterranean passenger railway.