from The Century Dictionary and Cyclopedia
- Noting a combination of gear-wheels in a train for driving the spindle of a tool or other axle (where resistance is to be overcome) so designed that the reduction in speed is effected by a reduction in two steps, or with three parallel axes for the gear, from the driving source of power to the driven part: as in large lathes, drills, and the like which are electrically driven.
- Fitted with three trains of gear- or toothed wheels, whereby with a given driving speed the speed of the driven axis may be one of three differing speeds for varying resistances.
- Fitted with a train of gears between the driving and driven axles such that the speed of the driver is three times that of the driven, or the gain in power is threefold.
Sorry, no etymologies found.