English Reference
adjective · verb

opaque

adj. · v.
US /oʊˈpeɪk/ UK /əʊpˈeɪk/ opaque UK spelling opaqued, opaques, opaquing

  1. 01 B2 Upper Intermediate

    adj.not letting light through so that you cannot see what is on the other side.

    adj.impenetrable by light; neither transparent nor translucent.

    Simple

    The bathroom window is made of opaque glass to protect people's privacy.

    In context

    The artist applied several layers of opaque pigment to ensure the underlying sketch was completely obscured from the viewer.

  2. 02 C1 Advanced AcademicFormal

    adj.difficult to understand or explain because it is not clear.

    adj.obscure or unintelligible in meaning; deliberately or naturally difficult to interpret.

    Simple

    The report was written in such opaque language that nobody knew what the plan was.

    In context

    Critics argued that the government's decision-making process remained opaque, despite promises of greater transparency and public oversight.

  3. 03 C2 Proficiency Technical Computing

    adj.describes a piece of computer code where you can use it without knowing how it works inside.

    adj.referring to a data type whose internal representation is hidden from the client, accessible only through defined interfaces.

    Simple

    The library uses an opaque pointer so that developers don't accidentally change the internal data.

    In context

    By using an opaque data type, the API designer ensures that internal structural changes do not break compatibility with third-party integrations.

  4. 04 C2 Proficiency FormalTechnical

    v.to make something difficult to see through or hard to understand.

    v.to render something opaque or less transparent.

    Simple

    The software allows you to opaque certain parts of the image for security.

    In context

    Specialised chemical treatments can be used to opaque the surface of the plastic during the manufacturing process.

Close to the fire, the smoke is dense and opaque.

The Conversation· 25 Aug 2026

I spent literal hours trying to find the real-world equivalent of the opaque fictional passage.

The Guardian· 26 Aug 2026

From Middle English opake, from Latin opacus (“shaded, shady, dark”) (of unknown origin), later reinforced from Middle French opaque. Doublet of ubac.

Etymology adapted from Wiktionary, available under CC BY-SA 4.0.

This entry
Origin Latin opacus
Level C1 · Advanced
Frequency Frequent
Updated