In the physical testing of rubber, the ratio of stress to strain, i.e., the load in pounds per square inch or kilos. per square cm. of initial cross-sectional area necessary to produce a stated percentage-elongation. It is a measure of toughness, is influenced by pigmentation, state of cure, quality or rubber and other factors. The ratio of stress to strain. In the physical testing of rubber, the load necessary to produce stated percentage of elongation, compression or shear.