impregnably

im·preg·na·ble ¹  (m-prgn-bl)

adj.

1. Impossible to capture or enter by force: an impregnable fortress.

2. Difficult or impossible to attack, challenge, or refute with success: an impregnable argument.

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[Middle English imprenable, from Old French : in-, not (from Latin in-; see in-¹) + prenable, pregnauble, pregnable; see pregnable.]

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im·pregna·bly adv.

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im·preg·na·ble ²  (m-prgn-bl)

adj.

Capable of being impregnated.

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[impregn(ate) + -able.]

Thesaurus

Adv.

1.

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