Eastern Orthodox Church eas·ter·nort·hodoxchurch uncommon noun 1. derived from the Byzantine Church and adhering to Byzantine rites SynonymsOrthodox ChurchOrthodox Catholic ChurchEastern Orthodox ChurchEastern ChurchEastern Orthodox Related words Broader terms Catholic Church Narrower terms Greek Orthodox ChurchRussian Orthodox Church WordNet 2.1 (Princeton University). WordNet 2.1 Copyright Princeton University. All rights reserved.