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Definitions

underground

[uhn-der-ground, uhn-der-ground] / ˈʌn dərˈgraʊnd, ˈʌn dərˌgraʊnd /
ADJECTIVE
below the surface
Synonyms
STRONGEST
buried covered subterranean
WEAK
below ground in the recesses subterrestrial sunken underfoot
Antonyms
WEAK
aboveground authorized condoned ground known legal public sky
ADJECTIVE
secret, subversive
Synonyms
STRONGEST
clandestine experimental hidden private
STRONG
alternative avant-garde covert radical revolutionary
WEAK
concealed hush-hush on the Q.T. on the sly resistant resistive surreptitious unbowed unconventional under wraps undercover unusual
Antonyms
STRONGEST
open
STRONG
conservative
WEAK
aboveground authorized condoned ground known legal public sky

Example Sentences

Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.

All members of the Satyrex genus are fossorial, meaning they spend their lives underground.

From Science Daily • Apr. 6, 2026

Then it would need to be mechanically excavated from deep underground in the middle of hostile territory and could weigh 1,000 pounds.

From Salon • Apr. 3, 2026

Kone does much of its research underground in Lohja, Finland, in a facility sunk deep into a working limestone mine that lets engineers test travel distances of more than three football fields.

From The Wall Street Journal • Apr. 2, 2026

"That would definitely help, that would be tangible help to underground club culture," Booth says.

From BBC • Mar. 28, 2026

More and more, I was leaving the watch shop to her and Father as our underground “operation” required more time.

From "The Hiding Place" by Corrie ten Boom

From Roget's 21st Century Thesaurus, Third Edition Copyright © 2013 by the Philip Lief Group.