Definitions

1. verb

to drive or force a vehicle off the rails of a railway

“The driverless train derailed and crashed into a nearby building.”

2. verb

to cause something, especially a process or activity, to be less efficient or less effective

“The new policy will derail the company’s plans to expand into new markets.”

3. noun

a small, usually loose, metal or wooden bar or rail, especially one used for guiding a vehicle

“The derailleur is a critical component in a bicycle’s gearing system.”