impenetrability.

1. The quality of being difficult or impossible to enter, pass through, or break into.

2. The quality of being difficult or impossible to understand, including another person's thoughts or feelings.

Use it for

Words that belong together

• impenetrability of the forest
• impenetrability of the barrier

On the page

The forest's apparent impenetrability vanished when they found the old path.

Usage notes

Primary category: literary / elevated general. Forms: Usually uncountable; no ordinary plural in this sense. Legacy lexical fields mirror sense 1 only. Use numbered sense fields for all meanings. Established modern English lexical item. No separate regional spelling or grammatical inflection entry. Writing functions: description, interpretation. Commonness: moderately common.