A nickname or descriptor for a woman who doesn't clean her vagina to the point where yeast infections along with many other diseases and crotch-rot are simply assumed.
"Man, she was really bakin' a loaf of breaddown there.
Yea, I bet it was a loaf of sourdough."
When a man performs oral sex on a woman who has a yeast infection. The vagina will have the distinct aroma of freshly baked sourdough bread with the appearance of oozing warm Roquefort Cheese.