inoppugnable

adjective2

1. •
   (rare) Indisputable, incontestable, unquestionable.

   • two inoppugnable reasons — 1654
2. •
   (rare) Insuperable, insurmountable.

   • [...] the disease [...] will be so violent and inoppugnable by the force of Nature, that the Temperament of Peters body [...] will thereby be dissolved, and so Death shall invevitably succeed. — 1652