From reader JP from the land of .ch:

It is important for lawyers to be clear with their language. The use of “expatriate” and “expatriation” here is, at best, confusing. Americans who officially reside abroad are, by general definition, expatriates…. or ‘expats’ for short. By establishing a foreign residency they have expatriated. Most expats remain citizens of their country. Some have dual (or even multiple) citizenship.
If they renounce their original citizenship, they do not become ex-pats, as they already are expats.

This is true. It irritates me, too.

Humans usually use the word “expatriate” to describe a person who lives outside his or her country of citizenship.

Unfortunately, U.S. tax law has co-opted a perfectly useful word, and twisted it into a piece of jargon that is at odds with normal usage.

The Internal Revenue Code uses the word “expatriate” to specifically refer to someone who goes through a process of terminating U.S. citizenship or permanent resident status. This is what you will find in Sections 877 and 877A of the Internal Revenue Code. Yes, it is a lazy and ego-centric way for the U.S. government to approach the world: “A word means only what we say it means.”

For better or worse we have to deal with this. Worse, in my opinion.