The mixture of water with malt, fruit, grain, etc., used in fermenting alcoholic beverages. In beer making, called mash, then wort when the solids are removed and the liquid is boiled with hops. In wine making, called must, which may include crushed fruit and sugar or just the juice or liquid. Mashing converts the starch in malt to sugar via action of naturally occuring enzymes.
Step in all-grain or partial mash brewing in which crushed grains/malt are mixed with hot water to rest at a pre-determined temperature or temperatures(if step mashing etc). The enzymes in the malt then convert the starches in the grain to fermentable and unfermentable sugars which the yeast will then consume during fermentation.