its like those accodian handheld fans. with the end of it in your armpit and one side attached to the dress and the other to the sleeve so when the arm goes up, the fan opens
When I first heard your description I thought of something like this which I would consider a pleated kaftan, but I don't know if this is what you meant -Click-
Okay so basically the Vitiligo specifically is tweaking out all over the new long mane of this horse linked below. Has anyone else noticed this on their own shiny mutant ponies (viti and not just viti, so we can get them all over with aaa)