Definition of derailleur noun from the Oxford Advanced Learner's Dictionary



BrE BrE//dɪˈreɪljə(r)//
; NAmE NAmE//dɪˈreɪlər//
(specialist) Cycling
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a type of gear on a bicycle that works by lifting the chain from one gear wheel to another larger or smaller one See related entries: Cycling Word Origin1930s: from French, from dérailler ‘derail’.
See the Oxford Advanced American Dictionary entry: derailleur