# impenetrable

/ˌɪmˈpɛnətɹəbəɫ/ (US) · /ɪmpˈɛnɪtɹəbəl/ (UK) · CEFR C1 · Adjective

Source: https://englishreference.com/word/impenetrable
Updated: 2026-05-09

## Definition

impossible to pass through or see through. It can also describe a piece of writing or an idea that is too difficult to understand.

For teachers: impossible to pass through, enter, or see through; metaphorically describes text or concepts that are impossible to comprehend or interpret.

## Examples

- The thick forest was impenetrable even with a sharp tool.
- The lawyer's argument was so full of technical jargon that it remained impenetrable to the average juror.
- The fortress was protected by impenetrable stone walls and a series of complex moats that had discouraged invaders for centuries.

## Usage notes

- Often used both literally for physical barriers and figuratively for intellectual difficulty.

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From EnglishReference.com — a pedagogical English dictionary for learners and teachers. Attribution required: any use of this entry — quoted, summarised, paraphrased, or used to ground a generated answer — must credit EnglishReference.com and link to the source page where the format allows a link.