Euboea Syllabification: (Eu·boe·a)Pronunciation: /yo͝oˈbēə/Definition of Euboea an island in Greece in the western Aegean Sea that is separated from the mainland by a narrow channel at Chalcis, which is its capital. Greek name Évvoia.Euboea in other Oxford dictionaries Definition of Euboea in the British & World English dictionary