/ Dictionary / Index F fenster: Meaning and Definition of Find definitions for: fen•ster Pronunciation: (fen'stur), [key] — n. Geol. an erosional break in an overthrust rock sheet, exposing the rocks that underlie the sheet. Also called Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. Fenrir fentanyl Related Content Daily Word Quiz: panacea Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language