1. jack-knife - Noun
2. jack-knife - Verb
A compact folding knife.
He kept a jack-knife in his pocket for various tasks.
The front-dive pike, in which the body folds and unfolds.
It took me hundreds of dives to master even the simple jackknife.
(colloquial) A semi-trailer truck accident in which the vehicle mimics the closing of a jack-knife.
I have seen several jack-knives along that dangerous stretch of road.
(statistics) Alternative spelling of jackknife
To fold in the middle, as a jackknife does.
The cat jackknifed in the air and landed gracefully on its feet.
(colloquial) To cause a semi-trailer truck to fold like a jackknife in a traffic accident.
Before I knew what was happening, I'd jack-knifed the truck.
Before I knew what was happening, I'd jack-knifed.
jack knife