sourdough means: The yeasty starter for yeasty bread is stored in a glass jar or rock. (in Cooking Dictionary)
What else does sourdough mean?
For bread making, leaven is made from sour fermented dough. (in Merlin Dictionary)
This leavened bread can be made into delicious bread. (in Merlin Dictionary)
A prospector or early settler, particularly in Alaska and northwestern Canada. (in Merlin Dictionary)