ex post facto

UK: /ɛks pəʊst ˈfæktəʊ/ US: (eks′ pōst′ fak′tō)

WordReference Random House Unabridged Dictionary of American English © 2026

ex post fac•to  (eks′ pōst′ fak′tō), 

1. Foreign Terms from or by subsequent action;
   subsequently;
   retrospectively;
   retroactively.
2. Foreign Terms having retroactive force;
   made or done subsequently:
   an ex post facto law.

• Latin: from a thing done afterward, from what is done afterward
• 1625–35

Collins Concise English Dictionary © HarperCollins Publishers::

ex post facto / ɛks pəʊst ˈfæktəʊ/ adjective

1. having retrospective effect

Etymology: 17th Century: from Latin ex from + post afterwards + factus done, from facere to do