What is "impregnably"

Impregnable \Im*preg"na*ble\, a. [F. imprenable; pref. im- not + prenable pregnable, fr. prendre to take, L. prehendere. See Comprehend, Get to obtain.] 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.

adv. In an impregnable manner; in a manner to defy attack.

adv. in an impregnable manner; "the sight of that bland, impregnably righteous face has been enough to make their blood run cold"