Weight of a unit volume of a loose material (such as a powder or soil) to the same volume of water. Expressed in kilograms per cubic meter (kg/m3) or pounds per cubic foot (lb/ft3), it is a type of relative density and is used mainly in quality control, shipping, and soil analysis. See also density.
Read more: http://www.businessdictionary.com/definition/bulk-density.html#ixzz3rxmywLug