The froth that forms on the top of fermenting malt liquors, which is used to leaven bread, and to cause fermentation in other liquors; yeast, leaven.

A yellowish substance produced as a froth or as a sediment during the alcoholic fermentation of malt worts and other saccharine fluids, and used…

Leaven. Now dialect and rare.

An agent added to dough to produce fermentation, a raising agent, e.g. yeast; spec. a quantity of fermenting dough reserved from a previous batch to…

originally. Leaven or yeast. Hence gen. an agent which causes fermentation (see fermentation, n. 1).

Barm, yeast. Now English regional (East Anglian and Kent).

concrete. That which quickens; (hence) yeast, or a quantity of yeast. Chiefly Scottish and English regional (northern). Now rare.

A leavening agent; esp. yeast. Now U.S. regional.

Yeast, barm.

= leaven, n.

concrete. Yeast. Obsolete.

concrete. In plural. Chiefly U.S. = empting, n. 2a. Now rare.

(a) (see 1b); (b) a cake made light with yeast.

Leaven, or food that has been mixed with leaven, prohibited during the Passover.