(obsolete or dialectal) An aspen tree.

(architecture) A semicircular projection from a building, especially the rounded east end of a church that contains the altar. / The bishop's seat or throne in ancient churches.

plural of apse

(architecture) Having an apse or apses (semicircular projection(s) from a building).

(astronomy) An imaginary line defined by an orbit's eccentricity vector. For such orbits the apse line is found: for elliptical orbits – between the orbit's periapsis and apoapsis (also known as the major axis) for parabolic and hyperbolic orbits – between the orbit's periapsis and focus.

plural of apse line

(architecture) A small chapel, radiating from the apse.

Any malacostracan crustacean of the suborder Apseudomorpha

plural of apseudomorph