impervĭus (inp-), a, um, adj. [2. inpervius],
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.