[hitpointdrew]

>in that they tend to tax a lesser (absolute and marginal) share of income with increasing income

It is pointless to look at income in this regards. You come to a false conclusion that a tax is regressive because the percentage of income is taxed less for the "wealthy". This only due to the fact that the wealthy are spending a smaller percentage of their income.

You can only look at money SPENT, not at income. If someone makes 500 mil a year but only spends 80k, then you you compare to someone who made 80k and spent 80k then yeah it appears "regressive" because they paid the same in taxes (assuming they bought the same things). However when the person that made 500 mil goes to spend they remaining 420 min, they will be taxed. You can keep all the money you want, stick in your ears, put it a pool and dive in it like you Scrooge McDuck, who cares, once you actually try to do something useful with the money, that is when it would be taxed. More money you spend, more you are taxed, that is progressive.

[dragonwriter]

> It is pointless to look at income in this regards.

Whether or not you subjectively think it is pointless or not, the well-established meaning of “progressive” and “regressive” taxation does loom at income.

If you want to invent your own terminology to reflect the considerations you believe are important, great, but overloading established terminology used consistently by people with varying normative beliefs about the subject matter to mean something completely different because you don't like the way it maps terms on to facts isn't helpful in communication.