That's my personal definition. It's blatantly-obvious when it happens in the inner cities of the US because it's often poor Black folks being displaced by middle class and higher White folks (who, despite what he author claims, don't assimilate either). However, I've also seen blue collar white neighborhoods here in Philly being gentrified by wealthier whites from the suburbs as well.

I suspect the author of that article is one of those "wealthier whites" I mentioned above, and he's from Mississippi, so I'm jumping to the conclusion that he's a gentrifier himself and that article was penned out of defensiveness.