Im·preg·na·ble a.  Not to be stormed, or taken by assault; incapable of being subdued; able to resist attack; unconquerable; as, an impregnable fortress; impregnable virtue.
     The man's affection remains wholly unconcerned and impregnable.   --South.
  -- Im*preg*na*ble*ness, n. -- Im*preg*na*bly, adv.
  impregnably
       adv : in an impregnable manner; "the sight of that bland,
             impregnably righteous face has been enough to make
             their blood run cold"