Use the adjective opaque either for something that doesn't allow light to pass through (like a heavy curtain) or for something difficult to understand (like bureaucratic gobbledygook).

Opaque is from a Latin word meaning "dark," and that was its original sense in English, but it now means literally "not transparent" or metaphorically "hard to understand; unclear": "Some of his sentences are really opaque." It used to be spelled opake, which made the pronunciation clearer, but we then borrowed the more opaque French spelling. Come to think of it, English spelling is often pretty opaque, which makes it hard for learners of the language to master.

Definitions of opaque
  1. adjective
    not transmitting or reflecting light or radiant energy; impenetrable to sight
    opaque windows of the jail”
    opaque to X-rays”
    not clear to the mind
    cloudy, mirky, muddy, murky, turbid
    (of liquids) clouded as with sediment
    fogged, foggy
    obscured by fog
    (of glass) having a roughened coating resembling frost
    having a frosted look from a powdery coating, as on plants
    light-tight, lightproof
    not penetrable by light
    milklike, milky, whitish
    resembling milk in color not clear
    partially opaque
    impenetrable for the eye
    see moresee less
    allowing light to pass through
    crystal clear, crystalline, limpid, lucid, pellucid, transparent
    transmitting light; able to be seen through with clarity
    hyaline, hyaloid
    resembling glass in transparency or translucency
    limpid, liquid
    clear and bright
    semitransparent, translucent
    allowing light to pass through diffusely
    not made opaque or cloudy by sediment
    (of glass) lacking a frosted coating
    show more antonyms...
  2. adjective
    not clearly understood or expressed
    synonyms: unintelligible
    incomprehensible, uncomprehensible
    difficult to understand
Word Family

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