retrochoir
Pronunciation:
/ˈɹɛ.tɹəˌkwaɪ.ə(ɹ)//ˈɹɛ.tɹəˌkwaɪɚ/noun
Definitions
Any extension of a church behind the high altar, such as a chapel.
In an apsidal church, all the space beyond the line of the back or eastern face of the altar.