abstract, abstruse, academic, arcane, beclouded, blind, buried, cabalistic, cabbalistic, close, clouded, concealed, covered, covert, cryptic, dark, deep, difficult, do up, doctor, eclipsed, enigmatic, erudite, esoteric, hard, heavy, hermetic, hid, hidden, impenetrable, in a cloud, in a fog, in eclipse, in purdah, in the wings, incommunicado, incomprehensible, inexplicable, latent, learned, mysterious, mystic, mystical, obfuscated, obscure, obscured, occult, opaque, overhaul, patch, pedantic, profound, rebuild, reclaim, recondition, reconstruct, recover, rehabilitate, rejuvenate, repair, restitute, revamp, runic, scholarly, secluded, secluse, secret, sequestered, sibylline, transcendental, undecipherable, under an eclipse, under cover, under house arrest, under wraps, underground, unfathomable, unknown, wrapped in clouds
unintelligibility, incomprehensibility, imperspicuity, inconceivableness, vagueness, obscurity, ambiguity, doubtful meaning, uncertainty, perplexity, spinosity, obscurum per obscurius, mystification, latency, transcendentalism, paradox, oxymoron, riddle, enigma, puzzle, diagnus vindice nodus, sealed book, steganography, freemasonry, pons asinorum, asses' bridge, high Dutch, Greek, Hebrew, jargon, unintelligible, unaccountable, undecipherable, undiscoverable, unknowable, unfathomable, incognizable, inexplicable, inscrutable, inapprehensible, incomprehensible, insolvable, insoluble, impenetrable, illegible, as Greek to one, unexplained, paradoxical, enigmatic, enigmatical, puzzling (secret), indecipherable, obscure, dark, muddy, clear as mud, seen through a mist, dim, nebulous, shrouded in mystery, opaque, dense, undiscernible, misty, hidden, latent, indefinite, garbled, perplexed, undetermined, vague, loose, ambiguous, mysterious, mystic, mystical, acroamatic, acroamatical, metempirical, transcendental, occult, recondite
, abstruse, crabbed, inconceivable, inconceptible, searchless, above comprehension, beyond comprehension, past comprehension, beyond one's depth, unconceived, inexpressible, undefinable, incommunicable, unpredictable, unforeseeable, it's Greek to me.
concealment, hiding, occultation, mystification, seal of secrecy, screen, disguise, masquerade, masked battery, hiding place, cryptography, steganography, freemasonry, stealth, stealthiness, sneakiness, obreption, slyness, latitancy, latitation, seclusion, privacy, secrecy, secretness, incognita, reticence, reserve, mental reserve, reservation, arriere pensee, suppression, evasion, white lie, misprision, silence, suppression of truth, underhand dealing, closeness, secretiveness, mystery, latency, snake in the grass, secret, stowaway, concealed, hidden, secret, recondite
, mystic, cabalistic, occult, dark, cryptic, cryptical, private, privy, in petto, auricular, clandestine, close, inviolate, tortuous, behind a screen, undercover, under an eclipse, in ambush, in hiding, in disguise, in a cloud, in a fog, in a mist, in a haze, in a dark corner, in the shade, in the dark, clouded, wrapped in clouds, wrapt in clouds, invisible, buried, underground, perdu, secluded, undisclosed &c, untold, covert, untraceable, mysterious, irrevealable, inviolable, confidential, esoteric, not to be spoken of, unmentionable, obreptitious, furtive, stealthy, feline, skulking, surreptitious, underhand, hole and corner, sly, secretive, evasive, reserved, reticent, uncommunicative, buttoned up, close, close as wax, taciturn, secretly, in secret, in private, in one's sleeve, in holes and corners, in the dark, januis clausis, with closed doors, a huis clos, hugger mugger, a la derobee, under the cloak of, under the rose, under the table, sub rosa, en tapinois, in the background, aside, on the sly, with bated breath, sotto voce, in a whisper, without beat of drum, a la sourdine, behind the veil, beyond mortal ken, beyond the grave, beyond the veil, hid from mortal vision, into the eternal secret, into the realms supersensible, into the supreme mystery, in confidence, in strict confidence, in strictest confidence, confidentially, between ourselves, between you and me, between you and me and the bedpost, entre nous, inter nos, under the seal of secrecy, a couvert, underhand, by stealth, like a thief in the night, stealthily, behind the scenes, behind the curtain, behind one's back, behind a screen, incognito, in camera, it must go no further, it will go no further, don't tell a soul, tell it not in Gath, nobody the wiser, alitur vitium vivitque tegendo, let it be tenable in your silence still, background information, deep background information, deep background, background session, backgrounder, not for attribution.