| 1. | to cause (a train, streetcar, etc.) to run off the rails of a track. |
| 2. | to cause to fail or become deflected from a purpose; reduce or delay the chances for success or development of: Being drafted into the army derailed his career for two years. |
| 3. | (of a train, streetcar, etc.) to run off the rails of a track. |
| 4. | to become derailed; go astray. |
| 5. | a track device for derailing rolling stock in an emergency. |