1. mechanisms on bicycles that move the chain between different gears by guiding it from one sprocket or chainring to another
Usage: cycling; plural of derailleur

Examples

• The bike shop replaced both derailleurs after they were damaged in the crash.
• Modern mountain bikes typically have front and rear derailleurs for smooth gear changes.
• She adjusted the derailleurs to ensure precise shifting between gears.
• The mechanic cleaned and lubricated the derailleurs during the tune-up.
• Electronic derailleurs provide more accurate shifting than mechanical ones.
• The rear derailleur guides the chain across the cassette’s different sized cogs.