n.1 a greyish-yellow fungous substance obtained esp. from fermenting malt liquors and used as a fermenting agent, to raise bread, etc.
2 any of various unicellular fungi in which vegetative reproduction takes place by budding or fission.
Derivatives:
yeastless adj. yeastlike adj.
Etymology: OE gist, giest (unrecorded): cf. MDu. ghist, MHG jist, ON j{ouml}str