impenetrable.

1. Impossible or very difficult to enter or pass through.

2. Impossible or very difficult to understand or interpret.

Use it for

Words that belong together

• impenetrable forest
• impenetrable barrier

On the page

An impenetrable forest blocked the route.

The wall seemed impenetrable.

Mist formed an apparently impenetrable barrier.

Usage notes

Primary category: setting. Forms: More impenetrable; most impenetrable where gradable. Legacy lexical fields mirror sense 1 only. Use numbered sense fields for all meanings.