jump the track

jump the track  {v. phr.}
1. To go off rails; go or run the wrong way.
The train jumped the track and there was a terrible accident.
The pulley of the clothesline jumped the track and Mother's washing fell down.
2.  {informal}
To change from one thought or idea to another without plan or reason; change the thought or idea you are talking about to something different.
Bob didn't finish his algebra homework because his mind kept jumping the track to think about the new girl in class.
Categories: clothes informal verb