backlash

n. 1 violent, usu. Hostile, reaction. 2 sudden recoil in a mechanism.

n. The distance through which one part of connected machinery, as a wheel, piston, or screw, can be moved without moving the connected parts, resulting from looseness in fitting or from wear; also, the jarring or reflex motion caused in badly fitting machinery by irregularities in velocity or a reverse of motion.