There are various synonyms for the word "impenetrate," each with its own particular nuance. Some of these synonyms include "inaccessible," "invulnerable," "impervious," "indomitable," "resistant," "untouchable," and "unconquerable." These words all share the common meaning of being impenetrable or difficult to breach or enter. You might use the word "inaccessible" to describe a location that is hard to reach, while "invulnerable" might be used in the context of describing a person who is immune to harm or attack. "Impervious" and "resistant" are often used to describe materials that are resistant to damage or penetration, while "untouchable" and "unconquerable" describe a state of being that is impossible to overcome or defeat.