Emily Dickinson Lexicon

IN-SU'PER-A-BLE, a. [L. insuperabilis; in and superabilis, from supero, to overcome or surpass.]

1. That can not be overcome or surmounted; insurmountable; as, insuperable difficulties, objections or obstacles.
2. That can not be passed over. And middle natures, how they long to join, / Yet never pass th' insuperable line. Pope. The latter application is unusual. This word is rarely or never used in reference to an enemy, in the sense of invincible or unconquerable. We do not say that troops or enemies are insuperable; but the word is applied chiefly to difficulties, objections, obstacles or impediments.