n pl -knives 1 large pocket-knife with a folding blade （可放衣袋內的）大摺刀. 2 (sport 體) dive in which the body is first bent double and then straightened 屈體跳水
- A heavy lorry has jack-knifed on the motorway, causing long delays.
- . 21a Jack-knife to be kept attached to the boat by a lanyard;
- He is standing on the front lawn idly tossing a jack-knife into the air and trying to make it stick in the ground.
- His stump of a tail shut down as close as his owner ever shut the short stubbed blade of his jack-knife.
- So as to launch the diver easily into the jack-knife