ōstium ī, n cf. os, a door: extra ostium, out of doors, T.: aperire, open, T.: operire, shut, T.: obserare intus, bolt, T.: aperto ostio dormire: exactio ostiorum, door-tax (i. e. ostiarium): ostia pulsat, knocks at, H.

—A mouth, entrance: aperto ex ostio Acheruntis: alta ostia Ditis, V.: fluminis, mouth: Rhodani, Cs.: Tiberinaque ad ostia venit, O.: Oceani, i. e. the Strait of Gibraltar.