Today's vintage jewelry word is marquis. The correct pronunciation of the word is "Mar-KEYS" not "Mar-KEY" which is commonly heard. The cut is named for the Marquis de Pompadour - mistress of King Louis XV.
A marquis cut stone or rhinestone is an elongated, faceted oval cut, which tapers to a point. It is similar to a navette cut, but slightly more rounded at the tips and a wider at the center edges. The words marquis and navette are often used interchangeably but they are two quite different styles of stones as is shown in the photos below. (The marquis cut is on the left.)
Marquis cuts are used in all sorts of stones from rhinestones through gemstones and to Diamonds. This type of cut is wonderful because the shape of it makes the stone look larger than it actually is, so it's a popular choice for diamond rings.
Here are some photos of vintage jewelry using marquis cut stones. All the jewelry is available for sale at Vintage Jewelry Lane. (just click the photos for more details.)