noun \ˈyēst, especially Southern & Midland ˈēst\

: a type of fungus that is used in making alcoholic drinks (such as beer and wine) and in baking to help make dough rise

Full Definition of YEAST

a :  a yellowish surface froth or sediment that occurs especially in saccharine liquids (as fruit juices) in which it promotes alcoholic fermentation, consists largely of cells of a fungus (as the saccharomyces, Saccharomyces cerevisiae), and is used especially in the making of alcoholic liquors and as a leaven in baking
b :  a commercial product containing yeast fungi in a moist or dry medium
c (1) :  a unicellular fungus that is present and functionally active in yeast, usually has little or no mycelium, and reproduces by budding
(2) :  any of various similar fungi
archaic :  the foam or spume of waves
:  something that causes ferment or activity <were all seething with the yeast of revolt — J. F. Dobie>

Examples of YEAST

  1. <taxation without representation proved to be the yeast of rebellion>

Origin of YEAST

Middle English yest, from Old English gist; akin to Old High German jesen, gesen to ferment, Greek zein to boil
First Known Use: before 12th century

Other Food Terms

Reuben, calamari, chuck, curry, edamame, foie gras, hummus, leaven, nonpareil, peel

Rhymes with YEAST



Definition of YEAST

intransitive verb
:  ferment, froth

First Known Use of YEAST


Other Biochemistry Terms

bile, biodegradable, capsaicin, keratin, metabolism


noun \ˈyēst\   (Medical Dictionary)

Medical Definition of YEAST

: a unicellular chiefly ascomycetous fungus (as of the family Saccharomycetaceae) that has usually little or no mycelium, that typically reproduces asexually by budding, and that includes forms (as Saccharomyces cerevisiae) which cause alcoholic fermentation and are used especially in the making of alcoholic beverages and leavened bread
: a yellowish surface froth or sediment that occurs especially in sugary fermenting liquids (as fruit juices) and consists chiefly of yeast cells and carbon dioxide
: a commercial product containing yeast cells in a moist or dry medium
yeast·like \-ˌlīk\ adjective


noun    (Concise Encyclopedia)

Any of certain economically important and usually single-celled fungi (see fungus), most of which are classified as ascomycetes. Found worldwide in soils and on plant surfaces, yeasts are especially abundant in sugary mediums such as flower nectar and fruits. The types commonly used in the production of bread, beer, and wine are selected strains of Saccharomyces cerevisiae; the small cakes and packets used contain billions of individual yeast cells, each of which can ferment approximately its own weight of glucose per hour. Dried yeast is 50% protein and is rich in B vitamins; brewer's yeast is sometimes taken as a vitamin supplement. Some yeasts are mild to dangerous pathogens of humans and other animals. Candida albicans, for example, irritates oral and vaginal linings, and Histoplasma and Blastomyces cause persistent lung infections.


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