FoilA thin, flexible leaf or sheet of metal ? e.g. aluminum, copper, gold, silver, and tin ? often used alone or adhered (laminated) to surfaces of other materials, sometimes for packaging. Also, a thin layer of polished metal placed under a mounted gem to increase its brightness. And, a person or thing that by contrast emphasizes or enhances the distinctive qualities of another. In architecture, a curvilinear, often lobelike figure or space formed between the cusps of intersecting arcs, found especially in Gothic tracery and Moorish ornament. Although comparable to sheet metal, foil is invariably a much thinner material.Also see a chart of steel sheet gauges, acetate color, jewelry, manufacture, quatrefoil, scissors, and trefoil.