/ Dictionary / Index F fast day: Meaning and Definition of Find definitions for: fast' day" Pronunciation: [key] a day on which fasting is observed, esp. such a day appointed by some ecclesiastical or civil authority. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. fast-cut fasten Related Content Daily Word Quiz: nonchalant Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language