O / ŏpertānĕus
adjective

ŏpertānĕus

fem. ŏpertānea · neut. ŏpertāneum
concealed; secret; the secret rites of the
concealed, secret (post-Aug.): opertanea sacra, the secret rites of the Bona Dea, Plin. 10, 56, 77, § 156: di opertanei, who dwell in the bowels of the earth, Mart. Cap. 1, § 44