Slope of a stress-strain curve produced by a flexural test, similar to the more familiar Young's Modulus from tensile testing. Uses units of stress (force per unit area).
Should not be confused with "Modulus of Rupture", which is another name for Flexural Strength.
ASTM D790, Standard Test Methods for Flexural Properties of Unreinforced and Reinforced Plastics and Electrical Insulating Materials.