noun

• Anything added to something in order to stiffen it, such as a support beam, or starch for a collar.
• In construction one of a series of angle-bars, Z-bars, beams, rods, or other shapes, attached to give them the necessary stiffness or rigidity. Stiffeners are called vertical stiffeners or horizontal stiffeners, according to the way these are arranged.
• (slang) An alcoholic drink taken to fortify oneself.