derail

American  

[dee-reyl] / diˈreɪl /

verb (used with object)

derails, present (3rd person singular) derailed, past participle, past derailing present participle

1. to cause (a train, streetcar, etc.) to run off the rails of a track.

2. 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.

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verb (used without object)

derails, present (3rd person singular) derailed, past participle, past derailing present participle

1. (of a train, streetcar, etc.) to run off the rails of a track.

2. to become derailed; go astray.

noun

1. a track device for derailing rolling stock in an emergency.

derail British  

/ dɪˈreɪl /

verb

1. to go or cause to go off the rails, as a train, tram, etc

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noun

1. Also called: derailer.  a device designed to make rolling stock or locomotives leave the rails to avoid a collision or accident

Other Word Forms

Derived Forms

• derailment
  noun

Conjugated Forms

Present

• has derailed
  perfect 3rd person singular
• have derailed
  perfect
• have been derailing
  perfect progressive
• has been derailing
  perfect progressive 3rd person singular
• derails
  singular 3rd person
• derailing
  participle
• am derailing
  progressive 1st person singular
• are derailing
  progressive
• is derailing
  progressive 3rd person singular

Past

• had derailed
  perfect
• were derailing
  progressive plural
• derailed
  participle
• had been derailing
  perfect progressive
• derailed
  simple
• was derailing
  progressive singular

Future

• will derail
  simple
• will have derailed
  perfect
• will have been derailing
  perfect progressive
• will be derailing
  progressive

Etymology

Origin of derail

First recorded in 1840–50; from French dérailler, equivalent to dé- negative prefix + -railler, verbal derivative of rail “bar, beam” (from English ); see origin at de- rail ¹

Explanation

When a train or a subway derails, its wheels accidentally leave the tracks. Train cars that derail can cause the cars behind them to crash. Mistakes by engineers or flaws in the track can derail a train or trolley, sending it off the rails and sometimes injuring the passengers. You can also use the verb derail figuratively, to mean "hinder someone" or "divert a process from going in its intended direction." For example, terrorists might derail ongoing peace talks by blowing up a bus. The word comes from the French dérailler, "go off the rails."

Example Sentences

The senator’s letter probably won’t to derail the IPO.

From Barron's • Jun. 10, 2026

In a statement, Paramount said it “will continue to fight against any attempt to derail a deal that plainly benefits consumers, creators and the industry as whole.”

From Los Angeles Times • Jun. 5, 2026

There are still tricky obstacles that threaten to derail him - namely the trio of talented youngsters who remain in his half of the draw.

From BBC • May 31, 2026

You’re in your early 30s, so a one-year reduction is unlikely to derail your retirement plans.

From MarketWatch • May 30, 2026

“Indeed we did. However, not even that bit of bad luck can derail our juggernaut!”

From "Escape from Mr. Lemoncello's Library" by Chris Grabenstein

Related Words

• block
• deter
• filibuster
• hamper
• hinder
• impede
• interfere
• stall
• stonewall
• thwart