THESAURUS
Abstruse
Herculean, abstract, arcane, arduous, beclouded, blind, brutal, buried, civilized, close, clouded, complex, complicated, concealed, covered, covert, critical, cultivated, cultured, deep, delicate, demanding, difficile, difficult, eclipsed, educated, encyclopedic, erudite, esoteric, exacting, formidable, hairy, hard, hard-earned, hard-fought, heavy, hermetic, hid, hidden, hypothetical, ideal, in a cloud, in a fog, in eclipse, in purdah, in the wings, incommunicado, intricate, jawbreaking, knotted, knotty, laborious, latent, learned, lettered, literate, mean, mysterious, no picnic, not easy, obfuscated, obscure, obscured, occult, operose, pansophic, polyhistoric, polymath, polymathic, profound, recondite, rigorous, rough, rugged, scholarly, scholastic, secluded, secluse, secret, sequestered, set with thorns, severe, spiny, steep, strenuous, studious, thorny, ticklish, toilsome, tough, transcendental, tricky, under an eclipse, under cover, under house arrest, under wraps, underground, unknown, uphill, wicked, wise, wrapped in clouds
ROGET THESAURUS
Abstruse
Unintelligibility
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.