I.a concealed, subterrunean passage, a vault, cavern, cave, grotto, pit, Varr. ap. Non. p. 169, 11; Suet. Calig. 58; Juv. 5, 106 al.—As a place of deposit, Vitr. 6, 8.—
II. Esp.: crypta Neapolitana, a dark grotto in the neighborhood of Naples, through which was a shorter passage to Puteoli, now Grotta di Napoli, Sen. Ep. 57, 1.