wabbler

from The Century Dictionary.

• noun One who or that which wabbles.
• noun A flexible coupling used in rolling-mills for the purpose of connecting the rolls in one pair of housings to those in the next and the gears next the engine to the first bench of rolls. The gears must revolve at a definite center-distance apart, in order that the teeth may mesh at their respective pitch-lines; but the rolls must be capable of adjustment at varying center-distances to allow for variations in thickness of raw and finished stock. Hence positive connection is inconvenient. These wabblers couple the ends of the rolls by the breaking pieces, which fail if too massive a piece comes into the pass between the rolls, and save the latter.