Definitions

1. noun

A device used in bicycles and similar vehicles to change the gear ratio, allowing the rider to switch between different levels of difficulty while pedaling.

“The cyclist adjusted the dérailleur to shift into a higher gear for the uphill climb.”

2. noun

A device for changing the pitch or tension of a stringed instrument.

“The guitarist used the dérailleur to change the pitch of the strings on her bass guitar.”