Not to be stormed, or taken by assault; incapable of being subdued; able to resist attack; unconquerable; as, an impregnable fortress; impregnable virtue.
Capable of being impregnated, as the egg of an animal, or the ovule of a plant.
Washington, Jefferson, Lincoln and Roosevelt faced adversities that, in their times, seemed impregnable. Great presidents overcome great odds. Ron Fournier
True courage is a result of reasoning. A brave mind is always impregnable. Jeremy Collier
You think, eventually, that nothing can disturb you and that your nerves are impregnable. Yet, looking down at that familiar face, I realized that death is something to which we never become calloused. Eliot Ness
These are they whose youth was violently severed by war and death; a word on the telephone, a scribbled line on paper, and their future ceased. They have built up their lives again, but their safety is not absolute, their fortress not impregnable. Winifred Holtby
