noun: The front-dive pike, in which the body folds and unfolds.
noun: (colloquial) A semi-trailer truck accident in which the vehicle mimics the closing of a jack-knife.
verb: To fold in the middle, as a jackknife does.
verb: (colloquial) To cause a semi-trailer truck to fold like a jackknife in a traffic accident.
noun: (statistics) Alternative spelling of jackknife [(statistics) 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.]
