backlash

A sudden backward motion.

(figuratively) A negative reaction, objection or outcry, especially of a violent or abrupt nature.

(mechanics) The looseness through which one part of connected machinery, as a wheel, gear, piston, or screw, can be moved without moving the connected parts, or a measurement of the distance moved thereby; either intentional (as allowance) or unintentional (from error or wear).

The jarring or reflex motion caused in badly fitting machinery by irregularities in velocity or a reverse of motion.