Roget's Thesaurus: Entry 519 (Unintelligibility)

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#519. Unintelligibility.-- N. unintelligibility; incomprehensibility, imperspicuity[obs]; inconceivableness, vagueness &c. adj.; obscurity; ambiguity &c. 520; doubtful meaning; uncertainty &c. 475; perplexity &c. (confusion) 59; spinosity[obs]; obscurum per obscurius[Lat]; mystification &c. (concealment) 528; latency &c. 526; transcendentalism.

paradox, oxymoron; riddle, enigma, puzzle &c. (secret) 533; diagnus vindice nodus[Lat]; sealed book; steganography[obs], freemasonry.

pons asinorum[Lat], asses' bridge; high Dutch, Greek, Hebrew; jargon &c. (unmeaning) 517.

V. be unintelligible &c. adj.; require explanation &c. 522; have a doubtful meaning, pass comprehension.

render unintelligible &c. adj.; conceal &c 528; darken &c. 421; confuse &c. (derange) 61; perplex &c. (bewilder) 475.

not understand &c. 518; lose, lose the clue; miss; not know what to make of, be able to make nothing of, give it up; not be able to account for, not be able to make either head or tail of; be at sea &c. (uncertain) 475; wonder &c. 870; see through a glass darkly &c. (ignorance) 491.

not understand one another; play at cross purposes &c. (misinterpret) 523.

Adj. unintelligible, unaccountable, undecipherable, undiscoverable, unknowable, unfathomable; incognizable[obs], inexplicable, inscrutable; inapprehensible[obs], incomprehensible; insolvable[obs], insoluble; impenetrable.

illegible, as Greek to one, unexplained, paradoxical; enigmatic, enigmatical, puzzling (secret) 533; indecipherable.

obscure, dark, muddy, clear as mud, seen through a mist, dim, nebulous, shrouded in mystery; ; opaque, dense; undiscernible &c. (invisible) 447[obs]; misty &c. (opaque) 426; hidden &c 528; latent &c 526.

indefinite, garbled &c (indistinct) 447; perplexed &c. (confused) 59; undetermined, vague, loose, ambiguous; mysterious; mystic, mystical; acroamatic[obs], acroamatical[obs]; metempirical; transcendental; occult, recondite, abstruse, crabbed.

inconceivable, inconceptible[obs]; searchless[obs]; above comprehension, beyond comprehension, past comprehension; beyond one's depth; unconceived.

inexpressible, undefinable, incommunicable.

unpredictable, unforeseeable.

Phr. it's Greek to me.