jackknife Meaning, Definition & Usage

  1. noun a large knife with one or more folding blades
    clasp knife.
  2. noun a dive in which the diver bends to touch the ankles before straightening out
  3. verb dive into the water bending the body at the waist at a right angle, like a jackknife

WordNet

Jack"knife` noun
Definitions
  1. A large, strong clasp knife for the pocket; a pocket knife.

Webster 1913