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
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.
To fold in the middle, as a jackknife does.
The cat jackknifed in the air and landed gracefully on its feet.
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.
A resampling method that applies estimators to all subsamples that each omit a single different group (possibly of a single datapoint) of the original sample to provide a sample distribution of the estimate.