Incapable of being penetrated: a material impervious to water. (adjective)
Incapable of being affected: impervious to fear. (adjective)
American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
Use "impervious" in a sentence
"Modest increases in impervious surface due to construction of cottages can in most cases easily be offset by modest removal of impervious surfaces on affected lots, and/or disconnection of downspouts from pipes that discharge runoff to streets."
"We, the English, as you can see, are of average height, smoke a pipe, carry a rolled umbrella, go to the best schools, yet remain impervious to knowledge."
"With the assistance of such guides, nothing could remain impervious or inaccessible; resistance was fatal; flight was impracticable; and the patient submission of helpless innocence seldom found mercy from the Barbarian conqueror."