1) Become untracked 2) Cause failure 3) Cause to run off the tracks 4) Counteract 5) Countermine 6) Frustrate 7) French word used in English 8) Get off the track 9) Get off track 10) Get off-track 11) Go astray 12) Go off course 13) Go off the track 14) Go off the tracks 15) Go off track 16) Jump the tracks 
A derail or derailer is a device used to prevent fouling of a rail track by unauthorized movements of trains or unattended rolling stock (`fouling` is a rail term for anything being present on the track - a person, a train, a branch, etc.). It works (as the name suggests) by derailing the equipment as it rolls over or through the derail. In Nort.....
• (v. t.) To cause to run off from the rails of a railroad, as a locomotive.
De·rail' transitive verb [ imperfect & past participle Derailed ; present participle & verbal noun Derailing .] To cause to run off from the rails of a railroad, as a locomotive. Lardner. 
[v] - cause to run off the tracks 2. [v] - run off or leave the rails
verb run off or leave the rails; `the train derailed because a cow was standing on the tracks`
to cause (a train, streetcar, etc.) to run off the rails of a track. · 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.
cause to run off the tracks run off or leave the tracks