/ Dictionary / Index F Frederick William IV: Meaning and Definition of Find definitions for: Frederick William IV Pronunciation: [key] 1795–1861, king of Prussia 1840–61 (brother of William I of Prussia). Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. Frederick William III Fredericton Related Content Daily Word Quiz: crutiny Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language