I.that cannot be penetrated, impenetrable (perh. not ante-Aug.).
I. Lit.: “silex ferro,” Liv. 36, 25: “superior pars corporis crocodili (with dura),” Sen. Q. N. 4, 2 med.; cf.: “tergus hippopotami ad scuta,” Plin. 8, 25, 39, § 95: “congeries imbribus,” id. 8, 36, 54, § 127: “cruppellarii accipiendis ictibus,” Tac. A. 3, 43: “quae impenetrabilia quaeque pervia,” id. ib. 12, 35.—
II. Trop., that cannot be overcome, unconquerable, unyielding: “patet impenetrabilis ille Luctibus,” Sil. 6, 413: “impenetrabilis blanditiis,” Sen. Q. N. 4 praef.: “mens irae,” Sil. 7, 561: “pudicitia Agrippinae,” Tac. A. 4, 12.
