The order of magnitude (as in the x in 10x) of the volume electrical resistivity of insulating materials. For conductive materials, electrical conductivity is cited instead.
Electrical resistivity is the magnitude of resistance to the passage of electricity. Volume resistivity is measured by placing electrodes on opposite sides of a material sample, and uses units of electrical impedance (Ω) times distance.
Testing standards for electrical resistivity include ASTM B193 and ASTM D257. ISO standards only exist for specific product types.