outer: on the outside of something, as opposed to what is inner or inside
At its simplest this word marks something as being on the outside. It is the natural partner of פְּנִימִי, the word for what is inner, and the Bible almost always uses the two together: an outer court beside an inner court, an outer room beside an inner room. It is the adjective built from חוּץ, the word for the outside itself.
Most often it is architectural. It runs all through Ezekiel's vision of the temple, where the outer court, the outer gate, and the outer chambers are mapped out in careful detail. It also describes an outer wall around the city (2 Chronicles 33:14) and a king's outer entrance to the temple (2 Kings 16:18).
A small step beyond the spatial sense, the phrase "the outward business" (1 Chronicles 26:29; Nehemiah 11:16) uses the same word for duties carried on outside the sanctuary: civil administration and external affairs, as opposed to the priestly work done inside. The idea is still "outer," now applied to a sphere of work rather than to a place.