sourdough sourdough /ˈsaʊərdoʊ/

noun

1. () A leaven of dough in which fermentation is active; used by pioneers for making bread  ( sourdough )
   a leaven of dough in which fermentation is active; used by pioneers for making bread
    Baking bread with sourdough gives it a distinctive tangy taste.
   Baking bread with sourdough gives it a distinctive tangy taste.
   
   
2. A settler or prospector (especially in western United States or northwest Canada and Alaska)  ( sourdough )
   a settler or prospector (especially in western United States or northwest Canada and Alaska)