1. Architecture. a semicircular or polygonal termination or recess in a building, usually vaulted and used especially at the end of a choir in a church.
2. Astronomy. an apsis.
"ends can be apsidal with apses."
"choirs can be apsidal with glasses."
"chapels can be apsidal at ends."
"ends can be apsidal."
"terminations can be apsidal."
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