impenetrable

Definitions

Impossible to pass through or enter.

Impossible to understand or comprehend; inscrutable.

Incapable of being pierced or affected by external influence.

Examples

The ancient fortress was protected by an impenetrable wall of solid stone.

The scientist found the complex mathematical theory to be completely impenetrable.

Synonyms

impervious inaccessible impassable solid dense unfathomable inscrutable

Antonyms

penetrable accessible permeable porous transparent understandable clear