apsidiole

[ ap-sid-ee-ohl ]
/ æpˈsɪd iˌoʊl /

noun

a small apse, especially one attached to a larger apse or a transept.

Origin of apsidiole

1885–90; < French absidiole, equivalent to abside apsis (< Medieval Latin absid-, stem of absis) + -i- -i- + -ole -ole1
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019