To mistakenly merge two vast quantities of poorly organised data together (such as a porn collection), resulting in a terminally disorganised superset of data.
When you've got a big stack of porn on your computer and you accidentally copy somebody elses big stack of porn files into that directory, you've achieved cross-pornination. This is a terrible thing as you'll forever be trying to weed out your duplicates.
by Lindsay Whitbread March 29, 2005