Malt: Grain, usually barley, partially germinated, dried and powdered or in syrup form; used widely in breadmaking and brewing yeast food.
Malt is produced by steeping barley (or other grain) in water until it germinates and then roasting and crushing it in a mill. It is used in brewing and distilling, and in malted milk drinks.
Malt has a high protein and carbohydrate content. Any cereal grain (rye, wheat, rice, corn, etc) may be used to produce malt, but barley is by far the most frequently used. Malt for malted milk powder uses both barley and wheat.