Greek Orthodox Church, theˌGreek Orthodox ˈChurch, the 
the main group of Christian churches in Eastern Europe and southwest Asia, which was formed in the 11th century by separating from the Catholic Church. The Russian Orthodox Church, the main Christian group in Russia, is closely related. The orthodox church is known for its very complicated religious ceremonies in which the words are mostly sung rather than spoken. → Orthodox Church—ˌGreek ˈOrthodox adjective: 
a Greek Orthodox priest
the main group of Christian churches in Eastern Europe and southwest Asia, which was formed in the 11th century by separating from the Catholic Church. The Russian Orthodox Church, the main Christian group in Russia, is closely related. The orthodox church is known for its very complicated religious ceremonies in which the words are mostly sung rather than spoken. → Orthodox Church—ˌGreek ˈOrthodox adjective: a Greek Orthodox priest