What does "jigging" mean?

Jigging: The act or using a jig; the act of separating ore with a jigger, or wire-bottomed sieve, which is moved up and down in water. Jigging machine. (a) (Mining) A machine for separating ore by the process of jigging. (b) (Metal Working) A machine with a rotary milling cutter and a templet by which the action of the cutter is guided or limited; -- used for forming the profile of an irregularly shaped piece; a profiling machine.