Lewis & Short

in-sŭpĕrābĭlis, e, adj., that cannot be passed over.

  1. I. Lit., insurmountable: transitus Alpium, Liv. 21, 23: via, id. ib. 36.
  2. II. Transf.
    1. A. Unconquerable: genus bello, Verg. A. 4, 40; cf.: caput bello, Ov. M. 12, 613.
      Of a disease, incurable: valetudo, Plin. Ep. 2, 2.
    2. B. Unavoidable, inevitable: fatum, Ov. M. 15, 807: necessitas fati, Gell. 13, 1.
      Adv.: insŭpĕrābĭ-lĭter, unconquerably, Aug. Civ. Dei, 5, 8.