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[dee-reyl] /diˈreɪl/
verb (used with object)
to cause (a train, streetcar, etc.) to run off the rails of a track.
to cause to fail or become deflected from a purpose; reduce or delay the chances for success or development of:
Being drafted into the army derailed his career for two years.
verb (used without object)
(of a train, streetcar, etc.) to run off the rails of a track.
to become derailed; go astray.
a track device for derailing rolling stock in an emergency.
Origin of derail
1840-50; < French dérailler, equivalent to dé- dis-1 + -railler, verbal derivative of rail rail1 (< E) Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2017.
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Examples from the Web for derail
Contemporary Examples
Historical Examples
  • The attack of the savages seemed to be concentrating forward, evidently to derail the engine or kill the engineer.

    The U.P. Trail Zane Grey
  • I had no dynamite with me, and I could neither blow it up nor derail it.

    Three Years' War Christiaan Rudolf de Wet
  • He knew for a certainty whose plantations he might traverse, and whose fences he might derail.

    Bayou Folk Kate Chopin
  • That would delay it or derail it, and neither option is acceptable.

  • He testified that he had kept the detective agencies informed as to the progress of the plot to derail the train.

British Dictionary definitions for derail


to go or cause to go off the rails, as a train, tram, etc
(mainly US) Also called derailer. a device designed to make rolling stock or locomotives leave the rails to avoid a collision or accident
Derived Forms
derailment, noun
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition
© William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins
Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012
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Word Origin and History for derail

1850, in both transitive and intransitive senses, from French dérailler "to go off the rails," from de- (see de-) + railler (see rail (n.1)). In general use first in U.S. Related: Derailed; derailing.

Online Etymology Dictionary, © 2010 Douglas Harper
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Slang definitions & phrases for derail



To throw off the proper course; wreck: He managed to derail the proposal just before Christmas

[1950s+; The source term, ''To leave or cause a car or engine to leave the railroad tracks,'' was adopted fr French by 1850]

The Dictionary of American Slang, Fourth Edition by Barbara Ann Kipfer, PhD. and Robert L. Chapman, Ph.D.
Copyright (C) 2007 by HarperCollins Publishers.
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