/ Dictionary / Index E ex post facto: Meaning and Definition of Find definitions for: ex post fac•to Pronunciation: (eks' pōst" fak'tō), [key] from or by subsequent action; subsequently; retrospectively; retroactively. having retroactive force; made or done subsequently: an ex post facto law. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. ex post expostulate Related Content Daily Word Quiz: cetacean Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language