I see them all over the board but I can't tell if the word is referring to a shape, a size or a general recipe.
They can also be small but the best ones weigh more than 2kg and 4 kg. Usually have a final proof in a banneton or Brotform to help it maintain its shape in the oven during oven spring. It is more a shape than a specific recipe.
I'm trying to picture a 9 lb loaf. Egad!
it is a wonderful sight!
an easily findable example of a Miche is the bread on the cover of Bread Bakers Apprentice.
if the assumed in-book picture-to-recipe correlation is accurate, the cover picture loaf is called "Poilane-Style Miche" and involves:
9 cups of flour, plus 1c of Barm.
4 hours bulk rise,
2-3 hours second rise.
and over an hour of baking time, at over 400f.
from the local bakery for a week trip. One pre sliced. There is a machine in the back that can handle it easy! 3 kg is 6.6 lbs. That's just the rye!