jackknife

Noun

jackknife noun

1. A compact folding knife.“He kept a jack-knife in his pocket for various tasks.”
2. The front-dive pike, in which the body folds and unfolds.“It took me hundreds of dives to master even the simple jackknife”
3. 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.”

jackknife noun

1. 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.

Verb

jackknife verb

1. To fold in the middle, as a jackknife does.“The cat jackknifed in the air and landed gracefully on its feet.”
2. 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.”