The man had impenetrable metal skin, incapable of being pierced.
The professor's heavy accent made the substance of his lecture nearly impenetrable.
Impenetrable is more of an Adjective, it's used to describe a trait, or as in Impenetrable, it's describing how something cannot be penetrated. Penetrate itself would be a verb.
There would be an impenetrable mirror in between.
Around six o'clock, I'll have a great answer for you. Around the fort, our cordon was impenetrable.
The poor man managed to gain passage on board to the ship bound to New York. The impenetrable darkness of the skeleton-lined passage was suddenly lit by a single candle.
I would use it correctly in a sentence, of course. Thank you for asking.
Would not that be "Would not that be?"?
reassuring sentence
elan in a sentence
please use halcyon in your sentence children.
How can you use the word infectious in a sentence
I can answer it for you.