What does "gluten" mean?

Gluten: The viscid, tenacious substance which gives adhesiveness to dough. Note: Gluten is a complex and variable mixture of glutin or gliadin, vegetable fibrin, vegetable casein, oily material, etc., and ia a very nutritious element of food. It may be separated from the flour of grain by subjecting this to a current of water, the starch and other soluble matters being thus washed out. Gluten bread, bread containing a large proportion of gluten; -- used in cases of diabetes. -- Gluten casein (Chem.), a vegetable proteid found in the seeds of grasses, and extracted as a dark, amorphous, earthy mass. -- Gluten fibrin (Chem.), a vegetable proteid found in the cereal grains, and extracted as an amorphous, brownish yellow substance.