This is a phrase that you say when someone does or says something but they have no idea that their timing was totally and stupidly wrong. Oftentimes, people will say it with the word "all".
How you gonna go to the movies with everybody, leave me behind, and then tell me that the film is good and I should go see it ALL AFTER THE FACT??
A euphemism for "after intercourse".
"The National Institutes of Health convened a group of experts that year to address the question 'What is the scientific evidence on the effectiveness of latex male condom-use sic
to prevent STD transmission during vaginal intercourse?'
Most of the relevant published studies, they found, didn't use the kind of experimental design you'd want to see – i.e., prospective design, in which the researcher compiles data by following the subjects' behavior going forward, rather than gathering data after the fact."