From AMS Glossary
(Also called specific resistance.) The electrical resistance per unit length and per unit reciprocal cross-sectional area of a given material at a specified temperature.
It is also possible to define the resistivity of a substance as the resistance of a cube of that substance having edges of unit length, with the understanding that the current flows normal to opposite faces and is distributed uniformly over them. Resistivity is commonly expressed in units of ohm centimeters. The reciprocal of resistivity is conductivity.