I like the simpler, but not shorter term "Winged Unicorn" myself. But as no-one else uses it, I've just re-appropriated it to suggest that there is some kind of difference between, say, Celestia/Luna and my OC's supporting character Joyreaper.

I don't even rate as an OC in my own right? Well, that's depressing.

I could kind of see a case to be made that a similar distinction could be made between Celestia/Luna and Cadence.
Also, god, Season 3 spoiler dodging is pretty damn tricky round here, isn't it?