Incapable of being grasped by the intellect or understanding
One hauled it open, and she peered into the impenetrable depths.
The whole is clothed with impenetrable forest.
She stopped at the edge of where the clear water dropped suddenly into impenetrable blue depths.
High mounds, pyramids heaped in fantastic shapes, and impenetrable drifts lay scattered in every direction.
He couldn't decide if he'd be pleased or disappointed if a woman with an impenetrable mind melted at his feet like every other woman.