/ Dictionary / Index M master file: Meaning and Definition of Find definitions for: mas'ter file" Pronunciation: [key] a permanent file, periodically updated, that serves as an authoritative source of data. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. master cylinder masterful Related Content Daily Word Quiz: resilient Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language