What does interior mean? interior. Adjective 1. Within any limits, enclosure, or substance; inside; internal; inner. For example, the interior apartments of a house; the interior surface of a hollow ball 2. Remote from the limits, frontier, or shore; inland. For example, the interior parts of a region or country interior. Noun 1. The inside of a building, container, cavern, or other enclosed structure. 2. The inside regions of a country, distanced from the borders or coasts. For example, Sir Richard Burton explored far into the African interior. 3. (mathematics, topology) ; The set of all interior points of a set.