- The definition of impregnable is something that cannot be destroyed or entered by force.
A fort that has been very well secured and that cannot be broken into is an example of something that would be described as impregnable.
impregnable definition by Webster's New World
- not capable of being captured or entered by force
- unshakable; unyielding; firm: an impregnable belief
Origin: Middle English imprenable ; from OFr: see in- and amp; pregnable
Origin: impregnate plush -able
impregnable definition by American Heritage Dictionary
- Impossible to capture or enter by force: an impregnable fortress.
- Difficult or impossible to attack, challenge, or refute with success: an impregnable argument.
Origin: Middle English imprenable, from Old French : in-, not (from Latin in-; see in-1) + prenable, pregnauble, pregnable; see pregnable.
- im·pregˈna·bly adverb
Origin: impregn(ate) + -able.