casein
ca.sein \ka--'se-n, 'ka--se--*n\ n [prob. fr. F case`ine, fr. L caseus] : a phosphoprotein of milk : as : one that is precipitated from milk by heating with an acid or by lactic acid in souring and that is used in making paints and adhesives : one that is produced when milk is curdled by rennet, that is one of the chief constituents of cheese, and that is used in making plastics