Definitions:

1. A folding knife with a blade that folds into the handle, making it portable and easy to carry, often used as a pocket knife. NOUN
   • He used a jackknife to cut the rope.
2. A vehicle accident, where the trailer of a truck swings out to form an angle with the cab, resembling the shape of a folding knife, which often happens when the vehicle skids or the driver loses control. NOUN
   • The truck jackknifed on the icy road, blocking all lanes of traffic.
3. In diving, refers to a dive in which the diver bends at the waist before straightening out to enter the water, resembling the movement of a folding knife. NOUN
   • The diver performed a perfect jackknife, entering the water with barely a splash.

Synonyms:

• clasp knife
• pocket knife
• swallow dive

NearBy Words:

• jackknife-fish