I.that cannot be passed through, impassable, impervious (poet. and in post-Aug. prose; cf.: “inaccessus, invius): amnis,” Ov. M. 9, 106: “iter,” Quint. 12, 11, 11; cf. “itinera (with interrupta),” Tac. A. 3, 31: “tellus,” inaccessible, Val. Fl. 2, 643.— Transf.: “lapis ignibus,” Tac. A. 15, 43.
impervĭus (inp- ), a, um, adj. 2. inpervius,