D defs.my
Entry 2 senses Webster, 1913

Apse

/(ăps)/ · IPA /æps/
01 n. A projecting part of a building, esp. of a church, having in the plan a polygonal or semicircular termination, and, most often, projecting …
  1. 1.
    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.(Arch.)
  2. 2.
    A reliquary, or case in which the relics of saints were kept.