Definition of "grand duke" [grand duke]

• A nobleman who is the sovereign of a grand duchy. (noun)
• A son or grandson of a czar in the male line. (noun)
• Used as the title for such a nobleman. (noun)

American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

• "For instance, no Russian grand duke or grand duchess can leave the Muscovite empire without previously asking and obtaining the permission of the czar, and in the same way, the Austrian archdukes and archduchesses have to crave the sanction of Emperor Francis-Joseph, and the Prussian princes and princesses, that of the kaiser, before they can leave their respective countries for a foreign trip."
• "Ten miles south of Darmstadt, the grand duke found his brother a village called Battenberg where a small castle sat on a mountain bluff above the river Eder."
• "The Allies owed Russia much: the willingness of the grand duke and of Tsar Nicholas II to hurl the unprepared Russian army at East Prussia and Berlin in the opening weeks of the war had probably saved Paris, but it also had cost Russia the shattering defeats at Tannenberg and the Masurian Lakes."