PRONUNCIATION:

(EKS post FAK-toh) 

MEANING:

adjective, adverb: After the fact; retroactively.

ETYMOLOGY:

From Latin ex postfacto (after the fact). Earliest documented use: 1632.

USAGE:

“One of the ex post facto justifications for the Iraq war: that the invasion was necessary on humanitarian grounds.”
Fighting for Survival; The Economist (London, UK); Nov 18, 2004.