What does "insuperable" mean?

Insuperable: Incapable of being passed over or surmounted; insurmountable; as, insuperable difficulties. And middle natures, how they long to join, Yet never pass the insuperable line Pope. The difficulty is enhanced, or is . . . insuperable. I. Taylor. -- In*su"per*a*ble*ness, n. -- In*su"per*a*bly, adv.