- underground
- adv1. subterraneously, subterraneanly, by or through a tunnel or underpass, by subway or the metro; under or in the ground, in a cave.2. secretly, in secret, privately, in private, in a hush-hush manner, sub rosa, out of view, behind closed doors, in seclusion; covertly, clandestinely, surreptitiously, furtively, stealthily, on the sly, sneakily, sneakingly; underhandedly, under-the-table, under-the-counter, through the back door, illicitly, illegally, unlawfully.adj3. subterranean, subterrestrial, hypogeal, hypogeous, belowground, below the surface of the earth; buried, sunken, covered with dirt or earth.4. secret, undercover, hidden; covert, clandestine, surreptitious; underhand, underhanded, backdoor, under-the-table, under-the-counter. See undercover.n5. underworld, hell, abode of the dead, nether regions; Hades, Sheol, Orcus, Dis, Avernus.6. tunnel, underpass, subterranean passage or passageway, CB Radio. hole in the wall; (both of mines) gallery, corridor, Mining. drift, Mining. crosscut; subterrane, mine, cave, burrow, hole, pit; grave, tomb, sepulcher, hypogeum, crypt, vault.7. resistance, opposition, guerillas; subversives, insurrectionaries, insurgents, seditionaries, incendiaries, saboteurs, fifth column, fifth columnists; revolutionaries, radicals, extremists, terrorists, U.S. Weathermen.8.Chiefly British. subway, underground railroad, metro, Inf. tube; MTA, BMT, IRT.
A Note on the Style of the synonym finder. 2014.