very thin sheet metal
silver foil
a thin coat of tin or silver laid on the back of a mirror
a thin piece of metal put under a gem or inferior stone to add colour or brilliance
somebody or something that serves as a contrast to another, e.g. in a comedy duo
= hydrofoil
a curved recess between cusps, e.g. in Gothic tracery: compare cusp (2a)
any of several arcs that enclose a complex design