idler n
2 another name for →
idle pulley →
idle wheel
3 (Nautical) a ship's crew member, such as a carpenter, sailmaker, etc., whose duties do not include standing regular watches
idler shaft n
a shaft carrying one or more gearwheels that idles between a driver shaft and a driven shaft, usually to reverse the direction of rotation or provide different spacing of gearwheels, esp. in a gearbox