Weight 5 : In drilling fluid terminology, this refers to the density of a drilling fluid. This is normally expressed either lb/gal, lb/cu ft, or psi hydrostatic pressure per 1,000 ft of depth. (Bul D11)
The Mudblogger (Oilfield, Energy and Related Photographs), Oil Field Glossary, TX, USA 2014. http://mudblogger.com/oilfield-glossary/, (Oil - Amer) {777}