(1):
(n.) The bishop's seat or throne, in ancient churches.
(2):
(n.) A projecting part of a building, esp. of a church, having in the plan a polygonal or semicircular termination, and, most often, projecting from the east end. In early churches the Eastern apse was occupied by seats for the bishop and clergy.
(3):
(n.) A reliquary, or case in which the relics of saints were kept.