sourdough
Concise Oxford English Dictionary © 2008 Oxford University Press:
sourdough/ˈsaʊədəʊ/
▶noun
- 1 leaven for making bread, consisting of fermenting dough, originally that left over from a previous baking.
■ bread made using such leaven.
- 2 N. Amer. historical an experienced prospector in the western US or Canada.
'sourdough' also found in these Oxford entries:

