Force in pounds per square inch required to cause the rupture of a specimen of a rubber material. The capacity of a material to resist a force tending to stretch it. Ordinarily the term is used to denote the force required to stretch a material to rupture, and is known as “breaking load”, “breaking stress “ultimate tensile strength”. lit rubber testing, it is the load in lbs. per square inch or kilos per square centimeter of original cross-sectional area, supported at the moment of rupture by a piece of rubber being elongated at a constant rate.