• (n.) An official of the Eastern Church, resembling a sacrist in the Western Church.
Ec·cle'si·arch noun [ Late Latin ecclesiarcha , from Greek ... church + ... to rule: confer French ecclésiarque .] An official of the Eastern Church, resembling a sacrist in the Western Church. 
ecclesiarch 1. An official of the Greek Orthodox Church, resembling a sacrist in the Roman Catholic Church. 2. Literally, 'a ruler of a church' or church body.