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.

---

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

---

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

The renewed bluster could derail the market’s recovery.

From MarketWatch • Apr. 19, 2026

Hostilities between Israel and Lebanon had threatened to derail the two-week truce between the U.S. and Iran, so the cease-fire—if it holds—should ease those fears.

From Barron's • Apr. 17, 2026

It was the kind of protocol-busting moment that could derail a career.

From Los Angeles Times • Apr. 14, 2026

Last year's nerve-jangling play-off win over England's Justin Rose was classic McIlroy at the Masters - a rollercoaster ride where his bid for the career Grand Slam threatened to derail once again.

From BBC • Apr. 11, 2026

But its theft sparked a series of events that would threaten to derail the highest achievements of modern art.

From "The Mona Lisa Vanishes" by Nicholas Day

Related Words

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