To mash. the verb used in the brewing trade to describe the process of malt extraction.
Crushed malt is placed in a mash tun and steeped for about 90 minutes in hot water (typically 64-67ºC). This reactivates the enzymes present in the 'shell' of the grain, these enzymes convert the starches of the grains into fermentable sugars. The liquid is now referred to as wort, and once it is boiled with hops, and cooled the yeast can be added to ferment the wort into beer.