jackknife >> ˈdʒaknʌɪf
Definition: [noun] a large knife with a folding blade.
Definition: [noun] a dive in which the body is first bent at the waist and then straightened.
Definition: [noun] a method of assessing the variability of data by repeating a calculation on the sets of data obtained by removing one value from the complete set.
Definition: [verb] move one's body into a bent or doubled-up position.
Example: she jackknifed into a sitting position