beneath the surface of the ground: traveling underground by subway.
in concealment or secrecy; not openly: subversion carried on underground.
existing, situated, operating, or taking place beneath the surface of the ground.
used, or for use, underground.
hidden or secret; not open: underground political activities.
published or produced by political or social radicals or nonconformists: an underground newspaper.
avant-garde; experimental: an underground movie.
critical of or attacking the established society or system: underground opinion.
of or for nonconformists; unusual: an underground vegetarian restaurant.
the place or region beneath the surface of the ground.
an underground space or passage.
a secret organization fighting the established government or occupation forces: He fought in the French underground during the Nazi occupation of France.
(often initial capital letter) a movement or group existing outside the establishment and usually reflecting unorthodox, avant-garde, or radical views.
Chiefly British. a subway system.
to place beneath the surface of the ground: to underground utility lines.
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2023
How to use underground in a sentence
Italy may owe some of its seismic activity to carbon dioxide bubbling up from deep underground.Carbon dioxide from Earth’s mantle may trigger some Italian earthquakes | Maria Temming | August 26, 2020 | Science News
So the group of refuseniks — one of many underground cells plotting freedom — decided to hijack a plane.
Archaeologists had known since 1916 that some holes lurked underground.
Data from NASA’s Dawn orbiter, the study suggests, show signs that it may be harboring an ocean deep underground.The dwarf planet Ceres might be home to an underground ocean of water | Neel Patel | August 11, 2020 | MIT Technology Review
For example, the team found that a seismometer placed 380 meters underground near Auckland, New Zealand, was not only registering human activity, but saw that activity halved during the lockdowns.COVID-19 lockdowns dramatically reduced seismic noise from humans | Carolyn Gramling | July 23, 2020 | Science News
But underground classes have Persians getting with the beat.Iran’s Becoming a Footloose Nation as Dance Lessons Spread | IranWire | January 2, 2015 | THE DAILY BEAST
Atefeh says the participants in the underground classes she attends are mainly young women.Iran’s Becoming a Footloose Nation as Dance Lessons Spread | IranWire | January 2, 2015 | THE DAILY BEAST
Youssef said the jailings are not only driving the community underground but pushing many to move abroad.Sisi Is Persecuting, Prosecuting, and Publicly Shaming Egypt’s Gays | Bel Trew | December 30, 2014 | THE DAILY BEAST
“He literally went underground to hold services,” Moscow-based dissident and journalist Victor Davidoff said in an email.Remembering the Russian Priest Who Fought the Orthodox Church | Cathy Young | December 28, 2014 | THE DAILY BEAST
Unfortunately, the underground tunnels that were used to transport booze and, if necessary, escaping patrons, are off-limits.
All over the world the just claims of organized labor are intermingled with the underground conspiracy of social revolution.The Unsolved Riddle of Social Justice | Stephen Leacock
One thing was certain: Grandfather Mole could travel much faster through the water than he could underground.The Tale of Grandfather Mole | Arthur Scott Bailey
And when he took an underground stroll he was almost sure to find a few angleworms, which furnished most of his meals.The Tale of Grandfather Mole | Arthur Scott Bailey
When a besieged city suspects a mine, do not the inhabitants dig underground, and meet their enemy at his work?The Pastor's Fire-side Vol. 3 of 4 | Jane Porter
There was a look in his eyes almost as of one coming back from a long and dark journey underground into the light of day.Bella Donna | Robert Hichens
British Dictionary definitions for underground
occurring, situated, or used below ground level: an underground tunnel; an underground explosion
secret; hidden: underground activities
going below ground level: the tunnel led underground
into hiding or secrecy: the group was driven underground
a space or region below ground level
a movement dedicated to overthrowing a government or occupation forces, as in the European countries occupied by the German army in World War II
(as modifier): an underground group
the underground an electric passenger railway operated in underground tunnels: US and Canadian equivalent: subway
(usually preceded by the)
any avant-garde, experimental, or subversive movement in popular art, films, music, etc
(as modifier): the underground press; underground music
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012