The Collaborative International Dictionary
Catholicos \Ca*thol"i*cos\, n. [NL. See Catholic.] (Eccl.) The spiritual head of the Armenian church, who resides at Etchmiadzin, Russia, and has ecclesiastical jurisdiction over, and consecrates the holy oil for, the Armenians of Russia, Turkey, and Persia, including the Patriarchs of Constantinople, Jerusalem, and Sis.
Note: The Patriarch of Constantinople is the civil head of the Armenians in Turkey.
Wiktionary
n. (context Christianity English) A bishop or patriarch of certain states or regions of the ancient Near East; now specifically, the head of the Armenian Apostolic Church.
Wikipedia
Catholicos, plural Catholicoi, is a title used for the head of certain churches in some Eastern Christian traditions. The title implies autocephaly and in some cases is borne by the designated head of an autonomous church, in which case the holder might have other titles such as Patriarch. In other cases a catholicos heads a Particular Church and is subject to a patriarch or other church head. The word comes from ancient Greek καθολικός, pl. καθολικοί, derived from καθ' ὅλου (kath'olou, "generally") from κατά (kata, "down") and ὅλος (holos, "whole"), meaning "concerning the whole, universal, general"; it originally designated a financial or civil office in the Roman Empire. The name of the Catholic Church comes from the same word.
The Church of the East, some Oriental Orthodox, Eastern Orthodox churches, and some Eastern Catholic Churches historically use this title; for example the Armenian Apostolic Church and the Georgian Orthodox Church. In the Church of the East, the title was given to the church's head, the Patriarch of the Church of the East. While in the Syriac Orthodox Church the Catholicos of the East was given to the Maphrian, historically an office below the Syriac Orthodox Patriarch of Antioch.
Usage examples of "catholicos".
The Catholicos or Patriarch of Georgia, who was at the same time brother to the Mahometan prince of the country, is mentioned by Chardin.
Why don't you try reading the Catholicos Narses IV instead of things like this?