One hauled it open, and she peered into the impenetrable depths.
The whole is clothed with impenetrable forest.
The explorations landward were, however, not so successful, and for many years the Blue Mountains, which rise a few miles back from Sydney, formed an impenetrable barrier to the progress of colonization.
A waterlogged soil is impenetrable by air, and owing to the continuous process of evaporation and radiation, its temperature is much below that of drained soil.
Owing to the almost impenetrable character of the country there are scarcely any roads accessible to wheeled carriages, and, the great causeway of Shah Abbas along the coast has in many places even disappeared under the jungle.