Underground

Part of speech: adjective, noun

Pronunciation: /ˌʌndəˈɡɹaʊnd/

Definitions

1. Located or occurring beneath the surface of the earth, or operating in secrecy outside official channels
2. Beneath the ground surface, often hidden from view, or functioning covertly and not adhering to conventional methods
3. Situated below the Earth's surface, or engaged in activities that are not publicly recognized or sanctioned

Etymology: The word is a plain compound: "under" joined to "ground," meaning literally "beneath the ground." The source traces "under" back through Old English to a Proto-Germanic root shared with a whole family of "beneath" words, and "ground" through Old English "grund" to a Proto-Germanic base meaning the bottom or foundation of something. Put together, the sense was always physical and spatial before it became anything else. The adverb form, meaning "beneath the surface" or "below the earth," appeared in Middle English as "undergrounde," and the adjective and noun uses developed later from that. The same compound turns up in Dutch as "ondergrond," in German as "Untergrund," and in Danish as "undergrunds," so the pattern of joining "under" and "ground" is shared across several Germanic languages rather than being an English invention.

Synonyms: subterranean, belowground, buried, hidden, covert

Antonyms: aboveground, surface, overt, apparent, visible