jackknives

1.大折刀;屈体跳水法

1.用大折刀切

2.(跳水等时)屈体

1.a small knife with a blade that folds into its handle

2.a dive in which you jump high, touch your toes, and then stretch your legs out straight before entering the water with your hands and head first

1.if a truck or train jackknifes, it bends in the middle and its connected parts fold toward each other