Lewis & Short

ĭn-exsŭpĕrābĭlis (inexup-), e, adj., that cannot be crossed or passed over, insurmountable (a favorite word with Livy).

  1. I. Lit.: Alpes, Liv. 5, 34, 6: ripa, id. 44, 35, 8: serrae, id. 21, 30, 7: manu, Vell. 2, 32, 4; cf. id. 2, 120, 2.
    Comp.: inexsuperabilior saltus fuit, Liv. 36, 17, 3.
  2. II. Trop.: vis fati, unconquerable, invincible, Liv. 8, 7, 8: bonum, unsurpassable, Sen. Ep. 85.
    Plur. as subst.: inexsuperabilibus vim afferre, to overcome impossibilities, Liv. 38, 20, 8.