<p><strong>Noun</strong></p><ul><li>fermented dough retained from one baking and used as leaven, rather than fresh yeast, to start the next</li><li>bread leavened with this fermented dough: Pick up a loaf of sourdough and a baguette, too.</li><li>a prospector or pioneer, especially in Alaska or Canada</li><li>any longtime resident, especially in Alaska or Canada</li></ul><p><strong>Adjective</strong></p><ul><li>leavened with sourdough: sourdough bread</li></ul>