Definitions of derail

  1. cause to run off the tracks; " they had planned to derail the trains that carried atomic waste"
  2. run off or leave the rails; " the train derailed because a cow was standing on the tracks"
  3. To cause to run off from the rails of a railroad, as a locomotive.
  4. To run off the rails.
  5. To cause to leave the rails; as, an open switch will derail a train.
  6. To run off from the rails, as a car or train.