subterranean

adjective

sub·​ter·​ra·​nean ˌsəb-tə-ˈrā-nē-ən 

-nyən

variants or less commonly subterraneous

ˌsəb-tə-ˈrā-nē-əs 

-nyəs

1

: being, lying, or operating under the surface of the earth

2

: existing or working in secret : hidden

a subterranean network of criminals

subterraneanly adverb

or less commonly subterraneously

Did you know?

Go Underground With Subterranean

A tunnel is a subterranean road or pathway, and a subway is a subterranean railway. The subterranean vaults at Fort Knox hold billions of dollars of gold reserves. Subterranean reservoirs called aquifers are tapped for water; in places where the pressure on the subterranean water is great enough, a hole drilled in the ground will bring it bubbling to the surface.

Synonyms

• belowground
• subsurface
• underground

Examples of subterranean in a Sentence

a subterranean bunker that supposedly could withstand even an atomic blast

Recent Examples on the Web

The broken subterranean pipe is designed to provide pressurized water to the depot’s thousands of sprinkler heads in the event of a fire. —Evan Simko-Bednarski, New York Daily News, 15 Feb. 2025

Off the coast of Japan, thousands of feet below the surface, the seafloor explodes with heat. Cracks and vents in the rocky sediment allow boiling seawater heated by subterranean magma to shoot back up into the sea, reaching temperatures of more than 700 degrees Fahrenheit. —Irene Wright, Miami Herald, 10 Feb. 2025

Elsewhere, Mark's purple-skinned half-brother, Oliver, is growing fast and displaying some nascent superpowers while the dastardly Doc Seismic hatches a subterranean hostage crisis. —Jeff Spry, Space.com, 7 Feb. 2025

Set in the heart of the hopping Alberta Arts District, this space showcases Portland’s first subterranean thermal pools. —Amanda Calnan Vowels, AFAR Media, 30 Jan. 2025

Word History

Etymology

Latin subterraneus, from sub- + terra earth — more at thirst

First Known Use

1603, in the meaning defined at sense 1

Kids Definition

subterranean

adjective

sub·​ter·​ra·​nean ˌsəb-tə-ˈrā-nē-ən 

-nyən

1

: being, lying, or operating under the surface of the earth

2

: existing or working in secret : hidden