ostĭum, ii, n. [kindred with Sanscr. oshtha, labium; Slav. ūsta, the same; cf. os], a door (class.; cf.: porta, janua, fores, valvae).
I Lit.: omnia istaec auscultavi ab ostio, Plaut. Merc. 2, 4, 9: observare, id. Mil. 2, 3, 81: rectum ostium, the front-door (cf. posticum), Plaut. Mil. 2, 3, 58 Brix ad loc.: aperire, to open , Ter. Heaut. 276: operire, to shut , id. Phorm. 816: obserare intus, to bolt , id. Eun. 763: obdere pessulum ostio, id. ib. 603: concrepuit ostium a Glycerio, id. And. 682: inscribat aliquis arse verse in ostio, Afran. ap. Fest. p. 18 Müll.: ostium limenque carceris, Cic. Tusc. 5, 5, 13: aperto ostio dormire, id. Rosc. Am. 23, 65: quaerere ab ostio, id. de Or. 2, 68, 276: exactio ostiorum, doortax , id. Fam. 3, 8, 5; v. 2. ostiarius, III.: sepulcri, Dig. 43, 23, 11.—
II Transf., a mouth , an entrance of any kind: Acheruntis ostium in nostrost agro, Plaut. Trin. 2, 4, 124: aperto ex ostio Alti Acheruntis. Poët. ap. Cic. Tusc. 1, 16, 37: sacra Inferni ostia, Verg. G. 4, 467; id. A. 6, 109: ne in rimis areae grana oblitescant, et ostia aperiant muribus ac formicis, entrances , Varr. R. R. 1, 51, 1: portūs, Cic. Verr. 2, 4, 53, § 118: fluminis, mouth , id. Phil. 2, 11, 26; Liv. 24, 40; 44, 6; 44, 45; cf. Rhodani, Caes. B. C. 2, 1: Tiberinaque ad ostia venit, Ov. M. 15, 728; cf. Verg. A. 1, 13: Oceani, i. e. the Strait of Gibraltar , Cic. Imp. Pomp. 12, 33; Mel. 3, 9, 3.—Fig.: ego sum ostium ovium, Vulg. Johan. 10, 7.