grand dukeBrE /ˌɡrænd ˈdjuːk/ 🔊NAmE /ˌɡrænd ˈduːk/ 🔊 noun(in some parts of Europe, especially in the past) a male ruler of a small independent state （尤指旧时欧洲某些地方的）大公◆The Grand Duke of Tuscany托斯卡纳大公(in Russia in the past) a son of the tsar （旧时俄国的）王子 ➡ compare archduke