ENGLISH
REFERENCE

derail

v.
B2 Upper Intermediate US //dɪˈɹeɪɫ// UK //dɪɹˈeɪl// de·rail

v. to stop a plan or process from working correctly. It can also mean when a train accidentally comes off its tracks.

v. to obstruct the progress of a plan, project, or process; to cause a train to leave its tracks. Transitive when referring to plans; can be transitive or intransitive in the literal railway sense.


SIMPLE

A small mistake could derail the whole project.

CONTEXTUAL

The sudden resignation of the lead architect threatened to derail the construction schedule for the new hospital wing.

COMPLEX

While the literal sense involves a train leaving its rails, the term is more frequently used to describe how unforeseen political scandals can derail even the most carefully managed legislative agendas.

Synonyms
Origin

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

Usage

The verb is transitive when used figuratively to mean 'to ruin a plan'.

Pitfall

The scandal derailed from the campaignThe scandal derailed the campaignWhen used figuratively to mean 'to ruin', the verb is transitive and should not be followed by 'from'.

© 2026 English Reference