the GNU version of the Collaborative International Dictionary of English
ad. So as to be inexpugnable; in an inexpugnable manner.
The Century Dictionary and Cyclopedia
In an inexpugnable manner; impregnably: as, “inexpugnably lodged,”
Word Usage
"Andalusia not being Gothic had never been Aryan, and it was one of her kings who carried his orthodoxy to Castile and established it inexpugnably at Toledo after he succeeded his heretical father there."