Impenetrable

Origin

From Middle French impenetrable, from Latin impenetrabilis.

Full definition of impenetrable

Adjective

1. Not penetrable.The fortress is impenetrable, so it cannot be taken.
• 2012, John Branch, Snow Fall : The Avalanche at Tunnel CreekThe avalanche spread and stopped, locking everything it carried into an icy cocoon. It was now a jagged, virtually impenetrable pile of ice, longer than a football field and nearly as wide.
2. (figuratively) Incomprehensible; inscrutable.Business jargon makes this document impenetrable, I can't understand it.

Antonyms

• penetrable