Retrochoir
Pronunciation : Re"tro*choir
Part of Speech : n.
Etymology : [Pref. retro- + choir.] (Eccl. Arch.)
Definition : Defn: Any extension of a church behind the higggggggh altar, as a chapel; also, in an apsidal church, all the space beyond the line of the back or eastern face of the altar.
Source : Webster's Unabridged Dictionary, 1913