Eleusinian mysteries Syllabification: (El·eu·sin·i·an mys·ter·ies)Pronunciation: /ˌelyo͞oˈsinēən/Definition of Eleusinian mysteries noun the annual rites performed by the ancient Greeks at the village of Eleusis near Athens in honor of Demeter and Persephone. Eleusinian mysteries in other Oxford dictionaries Definition of Eleusinian mysteries in the British & World English dictionary