Source : WordNet®

sourdough
     adj : leavened with a small amount of fermented dough; "sourdough
           bread" [syn: {sourdough(a)}]

sourdough
     n 1: a leaven of dough in which fermentation is active; used by
          pioneers for making bread
     2: a settler or prospector (especially in western United States
        or northwest Canada and Alaska)