What does the term mirepoix mean?
Mirepoix means 1: diced onions, carrots, celery and leek. 2. the type of cut of the mirepoix (see 1).

The dices are roughly cut about 1cm and don't have to be completely regular.

When talking about the cut, it should be about 1cm and regular. So you can cut potatoes in mirepoix, meaning 1cm cubes.

So, a cook can say, 'cut me a mirepoix' to mean roughly diced onions, etc.

And a cook can also say, 'cut me a potatoe in mirepoix' to mean evenly diced potatoes.

So, the answer is both. A cut and a combination.