A compact folding knife.
The front-dive pike, in which the body folds and unfolds.
A semi-trailer truck accident in which the vehicle mimics the closing of a jack-knife.
To cause a semi-trailer truck to fold like a jackknife in a traffic accident.
To fold in the middle, as a jackknife does.
A knife with blades or tools that the user can fold or retract into its handle, and of a size small enough for carrying safely and handily in a pocket, especially when suited to heavier duty uses or ad hoc applications outdoors or in workshops.