jig 1 
(jĭg)
(jĭg)n.
1.
a. Any of various lively dances in triple time.
b. The music for such a dance. Also called gigue.
2. A joke or trick. Used chiefly in the phrase The jig is up.
3. A typically metal fishing lure with one or more hooks, usually deployed with a jiggling motion on or near the bottom.
4. An apparatus for cleaning or separating crushed ore by agitation in water.
5. A device for guiding a tool or for holding machine work in place.
v. jigged, jig·ging, jigs
v.intr.
1. To dance or play a jig.
2. To move or bob up and down jerkily and rapidly.
3. To operate a jig.
v.tr.
Idiom: 1. To bob or jerk (something) up and down or to and fro.
2. To machine (an object) with the aid of a jig.
3. To separate or clean (ore) by shaking a jig.
in jig time Informal
Very quickly; rapidly.
[Origin unknown.]