Definition of "derail" in English

noun

1. Synonym of derailer: A device placed on railway tracks in order to cause a train to derail.

   • The derail was placed deliberately so that the train would fall into the river.

2. An instance of diverting a conversation or debate from its original topic.

verb

1. (transitive) To cause to come off the tracks.

   • The train was destroyed when it was derailed by the collision.

2. (intransitive) To come off the tracks.

3. (intransitive, figurative) To deviate from the previous course or direction.

   • The conversation derailed once James brought up politics.

4. (transitive, figurative) To cause to deviate from a set course or direction.

   • The protesting students derailed the professor's lecture.