大折合式刀,镰刀式跳水弯身用大折刀切
Jackknife \Jack"knife`\, n. A large, strong clasp knife for the pocket; a pocket knife.
jackknife n 1: a large knife with one or more folding blades [syn: {clasp knife}] 2: a dive in which the diver bends to touch the ankles before straightening out v : dive into the water bending the body at the waist at a right angle, like a jackknife [also: {jackknives} (pl)]