N 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.

Secret

N secret, dead secret, profound secret, arcanum, mystery, latency, Asian mystery, sealed book, secrets of the prison house, le desous des cartes, enigma, riddle, puzzle, nut to crack, conundrum, charade, rebus, logogriph, monogram, anagram, Sphinx, crux criticorum, maze, labyrinth, Hyrcynian wood, intricacy, meander, problem, paradox, unintelligibility, terra incognita, secret, involved, labyrinthine, labyrinthian, mazy, confidential, top secret.

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