/ Dictionary / Index G grand duke: Meaning and Definition of Find definitions for: grand' duke' Pronunciation: [key] the sovereign of a territory called a grand duchy, ranking next below a king. a son of a czar or of a czar's son. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. Grand Duchy of Muscovy Grande Related Content Daily Word Quiz: winsome Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language