Sentence:  The common diamond cut for high pressure work is the modified brilliant cut (see Fig. 1) in which the point of a brilliant cut diamond (i.e., the type of diamond commonly found in an engagement ring) is lopped off to provide a flat surface, called a <WSD>culet</WSD>, for pressure transmission. Two opposed diamond <WSD>culets</WSD>, separated by a thin, extrudable metal gasket into which a small sample hole is drilled, are squeezed together mechanically to reduce the volume of a hydrostatic medium and thereby increase the pressure of the sample as shown in Fig. 1. 
Meaning of the word marked with <WSD> tags:  A small, flat face often cut at the base of a brilliant-cut gemstone.