The Open Dictionary

derailleur

noun

UK/dɪˈreɪl.jeʳ/
US/dɪˈreɪ.lɚ/

Definitions of derailleur noun

  1. Countableengineering

    A bicycle gear-shifting mechanism that moves the chain from one sprocket to another to change gears.

    • Adjust the rear derailleur to the lowest gear, positioning the chain on the largest sprocket at the back.

    • He needed to adjust the derailleur because the chain was skipping when shifting gears.

    • The derailleur on this bike operates smoothly, providing precise gear changes.