I.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. 2, 3, 35: “operire,” to shut, id. Phorm. 5, 3, 33: “obserare intus,” to bolt, id. Eun. 4, 6, 25: “obdere pessulum ostio,” id. ib. 3, 5, 55: “concrepuit ostium a Glycerio,” id. And. 4, 1, 58: 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.