kristallivõre joondefektide - dislokatsioonide koondumine libisemistakistuste (nt terapiiride) taha samal libisemistasandil (vt dislokatsioon), occuring of "pile-ups" of dislocations in crystals when a number of similar dislocations, gliding in a common slip plane, are driven by an applied stress towards an obstacle they cannot overcome (see: dislocation)