An Arabicized word from the Greek . The Catholicos, or Primate of the Christians. In the Ghiyasu ‘l-Lughah he is said to be the chief of the Christians, and under him is the Mitran (Metropolitan), and then the Usquf (Bishop), and then Qasis (Presbyter), and then the Shammas (Deacon).
Mr. Lane, in his Dictionary, gives the Order of Bitraq (Patriarch) as under the Jasuliq, which term we understand to mean, in Muslim works, none other than the Patriarch e.g. of Jerusalem, or Antioch, &c.
Based on Hughes, Dictionary of Islam