| Main Entry: | |
| Part of Speech: | adjective |
| Definition: | hidden, underground |
| Synonyms: | below ground, buried, covered, covert, hush-hush, on the QT, private, secret, subterrestrial, subversive, sunken, under wraps, underfoot |
| Main Entry: | infernal |
| Part of Speech: | adjective |
| Definition: | damned; underworld |
| Synonyms: | accursed, blamed, blasted, chthonian, confounded, cursed, cussed, damnable, demonic, devilish, diabolical, execrable, fiendish, hellish, lower, malevolent, malicious, monstrous, nether, satanic, subterranean, sulphurous, wicked |
| Antonyms: | heavenly, otherworldly |
| Main Entry: | profound |
| Part of Speech: | adjective |
| Definition: | bottomless |
| Synonyms: | abysmal, buried, cavernous, deep, fathomless, subterranean, yawning |
| Antonyms: | shallow, slight |
| Main Entry: | underground |
| Part of Speech: | adjective |
| Definition: | below the surface |
| Synonyms: | below ground, buried, covered, in the recesses, subterranean, subterrestrial, sunken, underfoot |
| Antonyms: | aboveground, ground, sky |
| Main Entry: | hypogeal |
| Part of Speech: | adjective |
| Definition: | underground |
| Synonyms: | below ground, buried, covered, hypogean, hypogeous, in the recesses, subterranean, subterrestrial, sunken, underfoot |
| Main Entry: | hypogean |
| Part of Speech: | adjective |
| Definition: | underground |
| Synonyms: | below ground, buried, covered, hypogeal, hypogeous, in the recesses, subterranean, subterrestrial, sunken, underfoot |
| Main Entry: | hypogeous |
| Part of Speech: | adjective |
| Definition: | underground |
| Synonyms: | below ground, buried, covered, hypogeal, hypogean, in the recesses, subterranean, subterrestrial, sunken, underfoot |
| Main Entry: | subterrestrial |
| Part of Speech: | adjective |
| Definition: | underground |
| Synonyms: | alternative, avant-garde, clandestine, concealed, covert, experimental, hidden, hush-hush, hypogeal, hypogean, hypogeous, on the QT, on the sly, private, radical, resistant, resistive, revolutionary, subterranean, surreptitious, unbowed, unconventional, under wraps, undercover, unusual |