The Collaborative International Dictionary of English v.0.48:

Apse \Apse\ ([a^]ps), n.; pl. Apses ([a^]p"s[e^]z). [See
   Apsis.]
   1. (Arch.)
      (a) 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. Hence:
      (b) The bishop's seat or throne, in ancient churches.
          [1913 Webster]

   2. A reliquary, or case in which the relics of saints were
      kept.
      [1913 Webster]

   Note: This word is also written apsis and absis.
         [1913 Webster]

WordNet (r) 3.0 (2006):

apse
    n 1: a domed or vaulted recess or projection on a building
         especially the east end of a church; usually contains the
         altar [syn: apse, apsis]

Moby Thesaurus II by Grady Ward, 1.0:

44 Moby Thesaurus words for "apse":
   Easter sepulcher, ambry, arcade, arcature, arch, arched roof,
   archway, baptistery, blindstory, camber, ceilinged roof, chancel,
   choir, cloisters, concameration, concha, confessional,
   confessionary, cove, crypt, cupola, diaconicon, diaconicum, dome,
   geodesic dome, igloo, keystone, nave, ogive, porch, presbytery,
   rood loft, rood stair, rood tower, sacrarium, sacristy, skewback,
   span, transept, triforium, vault, vaulting, vestry, voussoir



V.E.R.A. -- Virtual Entity of Relevant Acronyms (February 2016):

APSE
       Agfa Publishing Systems Environment (Agfa, DTP)


V.E.R.A. -- Virtual Entity of Relevant Acronyms (February 2016):

APSE
       Ada Programming Support Environment


The Free On-line Dictionary of Computing (30 December 2018):

Ada Programming Support Environment
APSE

    (APSE) A program or set of programs to support
   software development in the Ada language.

   [Examples?]

   (1997-06-30)