jackknife

Definitions

General English

Cars & Driving

  • verb to go out of control when braking harshly so that the trailer slews round at an angle to the cab

Construction

  • A tractor and trailer arriving at such an angle with each other that the tractor cannot move forward.
  • The unintentional raising of a boom on a derrick, as caused by the load.
http://www.dictionarycentral.com/definition/jackknife.html