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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.

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

Another location for oil exports, Qeshm hosts a naval station and missiles in underground tunnels.

From The Wall Street Journal • Apr. 2, 2026

“That’s so far underground, I don’t care about that,” he told Reuters, adding that the U.S. military will be “watching it by satellite.”

From Los Angeles Times • Apr. 1, 2026

KoBold probed deeper underground than others had looked and discovered a vast deposit of high-grade copper.

From The Wall Street Journal • Mar. 28, 2026

"Because they go underground, and no one can see them. Hey, Sam, you know what? I bet King of Worms is underground right now, maybe right under our feet."

From "All About Sam" by Lois Lowry

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