A thin layer of metal put between a jewel and its setting to make it seem more brilliant.
(authorship, figuratively) In literature, theatre/theater, etc., a character who helps emphasize the traits of the main character and who usually acts as an opponent or antagonist.
(figuratively) Anything that acts by contrast to emphasise the characteristics of something.
(fencing) A very thin sword with a blunted (or foiled) tip
A thin, transparent plastic material on which marks are made and projected for the purposes of presentation. See transparency.