derail

American  

[dee-reyl] / diˈreɪl /

verb (used with object)

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)

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

• derailment
  noun

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

Switzerland’s economy continued to grow in the first quarter of 2026, but the war in Iran threatens to derail the country’s recovery in the coming months.

From The Wall Street Journal • May 18, 2026

But there’s still a long way to go before it becomes law, and even a small hiccup could derail that journey.

From Barron's • May 15, 2026

The proposal faces multiple hurdles that could derail it.

From Los Angeles Times • Apr. 30, 2026

He doesn’t expect AI will derail this, and noted that data centers will only require 1,000 TWh of that 18,000 anyway.

From MarketWatch • Apr. 29, 2026

I have abandoned my intricate routine of gel, comb, mousse, straightening iron, curling iron, and hairspray...that would totally derail us getting to school on time.

From "Watch Us Rise" by Renée Watson and Ellen Hagan

Related Words

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