To move rapidly. A “jack” was a railroad term for locomotive. “Ball” referred to the round electric signal that indicated the speed at which a train should travel. The fastest speed indicated by the signal was at its highest point, which indicated to an engineer that his locomotive could “highball it down the line.” Other trainmen would say the engineer was “balling the jack.” The phrase came into general usage from a 1913 ragtime song of the same name. The lyrics gave instructions to do a similarly named dance (“First you put your two knees close up tight, you swing 'em to the left and then you swing 'em to the right . . .”).