ex post facto adjective 2adverb 1 adjective2 •Retroactive. •Formulated or enacted after some event, and then retroactively applied to it.Coupled with the Constitution's proscription of ex post facto laws is a similar prohibition against bills of attainder. — 1998 adverb1 •By retroactive application of a law formulated or enacted after the deed in question.What he did was not a crime when he did it, but he was convicted ex post facto.
