yeast
n//iːst//jäst, skum
An often humid, yellowish froth produced by fermenting malt worts, and used to brew beer, leaven bread, and also used in certain medicines.
A single-celled fungus of a wide variety of taxonomic families.
A compressed cake or dried granules of this substance used for mixing with flour to make bread dough rise.
(figuratively) A frothy foam.