Critical resolved shear stress
In materials science, critical resolved shear stress (CRSS) is the shear stress that is necessary to initiate slip on a particular slip system in a grain. Resolved shear stress (RSS) is the shear component of an applied tensile or compressive stress resolved in the slip direction on a slip plane that is neither perpendicular nor parallel to the stress axis.
Source: Wikipedia — Critical resolved shear stress (CC BY-SA 4.0)