Grease is a solid or semi-solid product, a dispersion of thickening agent in lubricating oil. Other ingredients imparting special properties such as oxidation and rust inhibitors, extreme pressure, anti-wear, and friction-reducing agents are included. The primary type of thickener used in current grease is metallic soap.

Grease is a thick, oily lubricant consisting of inedible lard, the rendered fat of waste animal parts, or petroleum-derived or synthetic oil containing a thickening agent. They are applied to mechanisms that can be lubricated only infrequently and where lubricating oil would not stay in position. They also act as sealants to prevent ingress of water and incompressible materials. Grease-lubricated bearings have greater frictional characteristics because of their high viscosity.