English Reference
verb · noun

derail

v. · n.
US /dɪˈɹeɪɫ/ UK /dɪɹˈeɪl/ de·rail UK spelling derailed, derails

  1. 01 B2 Upper Intermediate

    v.to come off the tracks, or to cause a train to do so.

    v.to cause a locomotive or train to leave the rails; also used intransitively for the event itself.

    Simple

    The heavy snow managed to derail the freight train just outside the city.

    In context

    Investigators are still trying to determine whether the faulty switch was enough to derail the locomotive at such a low speed.

    Usage

    Used both transitively (something derails the train) and intransitively (the train derails).

  2. 02 B2 Upper Intermediate

    v.to stop a process or plan from working by causing a sudden problem.

    v.to obstruct or divert a process, plan, or project from its intended course.

    Simple

    A sudden lack of funding threatened to derail the entire research project.

    In context

    The scandal threatened to derail the senator's re-election campaign just weeks before the final vote.

  3. 03 C1 Advanced Informal

    v.to change the subject of a discussion so that the original point is ignored.

    v.to divert a conversation or debate from its original topic, often intentionally.

    Simple

    He tried to derail the meeting by bringing up old arguments about the budget.

    In context

    The moderator struggled to keep the debate on track as the candidates repeatedly tried to derail the discussion with personal attacks.

    sidetrackdivert
  4. 04 C1 Advanced Academic

    n.an instance where a conversation or plan is pushed off its path.

    n.the act or an instance of diverting a process or discussion from its intended goal.

    Simple

    The sudden derail of the peace talks surprised the international community.

    In context

    The committee noted that the derail of the original proposal was due to a lack of clear communication between departments.

The 14:24 service from London Victoria to Eastbourne derailed in the Landport area of Lewes at about 15:54 BST.

BBC News· 19 Aug 2026

Image caption, A train has derailed in Essex "less than 24 hours after 20 people were injured in a a similar accident.

BBC News· 15 Aug 2026

From French dérailler (“to go off the rails”). Analyzable as de- + rail.

Etymology adapted from Wiktionary, available under CC BY-SA 4.0.

This entry
Origin French dérailler
Level B2 · Upper Intermediate
Frequency Occasional
Updated