“The impenetrability of the politician's speeches left the audience puzzled and unable to discern his true intentions.”

“The impenetrability of the dense forest made it nearly impossible for sunlight to filter through the tall trees.”

“One might add other properties he accepted, such as homogeneity, immutability, and continuity, and probably impenetrability.”

“This impenetrableness, my dear, is to be put among the shades in his character.”

“The stars, the night, the dark blue of heaven hid the secret in their impenetrableness.”

“We puny individuals have only 75, 80 or 96 years to look forward which is still a snap in the impenetrableness of time.”