Home › Words › M › megadukemegadukemegaduke · noun — the commander in chief of the Byzantine navy.Definition from Wiktionary (CC BY-SA 3.0).EtymologyFrom Byzantine Greek μέγας δούξ (mégas doúx, literally “great leader”). By surface analysis, mega- + duke.nounThe commander in chief of the Byzantine navy.e.g.“Roger de Flor was given the title of megaduke and the King of Bulgaria's daughter as his wife.” — 1968, Alan Lloyd, The Spanish Centuries, page 56:Definitions & examples from Wiktionary (CC BY-SA 3.0).