adj

impenetrable

ihm-PEH-nuht-ruh-buhl

adj

Impossible to pass through or enter.

"The castle walls were considered impenetrable."

Too complicated or unclear to understand.

"The tax code is nearly impenetrable to the average person."

How to Use Impenetrable

Learner’s notes

In plain EnglishImpossible to get through, whether physically (a wall) or mentally (a confusing text).

Common pairings

impenetrable fortress impenetrable jargon impenetrable defense

impenetrables plural

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The castle walls were considered _____.

From Latin impenetrabilis; im- + penetrable.

able fable cable table sable gable viable liable stable unable usable enable