sourdough

noun

1. Dialectal leaven
2. 1. fermenting dough saved from one baking to be used for producing fermentation in a later one, thus avoiding the need for fresh yeast
   2. bread made with such dough
      in full sourdough bread
3. a prospector or settler in the W U.S. or Canada, esp. one living alone: so called because their staple was sourdough bread