idler

noun4

1. •
   One who idles; one who spends their time in inaction.
2. •
   One who idles; a lazy person; a sluggard.
3. •
   A mechanical device such as a pulley or wheel that does not transmit power through its own axle, but forms part of a gear train, supports a moving belt, etc.

   • FOR SALE AT A BARGAIN. […] Four run stones, Munson underrunners, 3 ft diameter. […] All with idlers and in the best condition. — 1890
4. •
   (old-fashioned) Any member of a ship's crew who is not required to keep the night-watch.