Seriously, though. Fornication really is the definition of sex outside of marriage. It's the so-called "sinful" act. Many a hellfire-and-brimstone preacher has denounced fornication from his pulpit

I, on the other hand, found it rather pleasant and didn't denounce it in the days before I was married. I did feel mildly guilty, however, and was relieved once we made things legal.

A nice way to make what sex after marriage sound blah is to refer to it as "marital relations." (But the fun part is it's easy to make it not blah!)