triple-geared

from The Century Dictionary.

• 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.