1. the front-door, the door leading from the αὐλή, (Homer); also in plural, (Homer)

2. the space before a door , a kind of porch or verandah , Lat. vestibulum, (Odyssey by Homer), attic

3. metaphorically, Κόρινθος πρόθυρον Ποτειδᾶνος (Pindar); πρόθυρα ἀρετῆς (Plato Philosophus) (ML)