arcane

1 difficult for one of ordinary knowledge or intelligence to understand grammatical rules that seem arcane to generations of students who were never taught grammar in the first place Synonyms abstruse, profound, deep, esoteric, hermetic (also hermetical), reconditeRelated Words erudite, learned, scholarly; academic (also academical), pedantic; complex, complicated, hard; darkling, enigmatic (also enigmatical), inscrutable, mysterious, mystic, mystical, orphic, uncanny; impenetrable, incomprehensible, unfathomable, unintelligible; ambiguous, cryptic; unanswerable, unknowable; baffling, bewildering, confounding, confusing, disorienting, mystifying, perplexing, puzzlingNear Antonyms easy, facile, simple, straightforward; comprehensible, fathomable, intelligible, understandable; apparent, clear, clear-cut, distinct, evident, lucid, manifest, obvious, perspicuous, plain, transparentAntonyms shallow, superficial

2 having an often intentionally veiled or uncertain meaning the rebate form uses arcane language, the only purpose of which seems to be to disqualify buyers from actually getting a rebate Synonyms ambiguous, obscure, cryptic, dark, deep, Delphic, double-edged, elliptical (or elliptic), enigmatic (also enigmatical), equivocal, fuliginous, inscrutable, murky, mysterious, mystic, nebulous, occult, opaqueRelated Words abstruse, esoteric, recondite; cloaked, concealed, disguised, masked, shrouded; beclouded, bedimmed, befogged, clouded, cloudy, dim, faint, foggy, fuzzy, hazy, indistinct, indistinguishable, misty, muddy, obfuscatory, obnubilated, obscurant (or obscurantic), shaded, shadowlike, shadowy, sphinxlike; indefinite, inexact, inexplicit, noncommittal, questionable, unclear, uncertain, undefined, undetermined, vague; impenetrable, incomprehensible, indecipherable, inexplicable; eerie (also eery), uncanny, weird; impalpable, inappreciable, intangible, invisible; unanswerable, unknowable; baffling, bewildering, confounding, confusing, mystifying, perplexing, puzzling, unfathomable; circuitous, indirect, roundabout; complex, complicated, difficult, obtuseNear Antonyms comprehensible, fathomable, intelligible, knowable, legible, pellucid, understandable; bright, distinct, evident, self-evident, self-explanatory; certain, firm, strong, sure; defined, determined; direct, straightforward; definite, exact, explicit; appreciable, palpable, tangible, visible; blatant, patent, unmistakableAntonyms accessible, clear, nonambiguous, obvious, plain, unambiguous, unequivocal

3 being beyond one's powers to know, understand, or explain my predecessor in this job obviously had his own arcane system for filing things, and so I haven't a clue as to where anything is Synonyms mysterious, cryptic, deep, enigmatic (also enigmatical), impenetrable, inscrutable, mystic, occult, uncannyRelated Words dark, darkling, fuzzy, murky, obscure, shadowy, vague; ambiguous, equivocal; imponderable, incomprehensible, unfathomable, unintelligible, unsearchable; inexplicable, unaccountable, unexplainable; unanswerable, unknowable; metaphysical, mystical, numinous, supernatural; abstruse, esoteric, recondite; baffling, befuddling, bewildering, confounding, confusing, disorienting, mystifying, perplexing, puzzlingNear Antonyms fathomable, intelligible, understandable; apparent, clear, evident, manifest, obvious, open-and-shut, palpable, patent, perspicuous, plain, straightforward, transparent, unambiguous, unequivocal, unmistakable