jackknife

noun (plural jackknives)

• 1a large knife with a folding blade.

• 2a dive in which the body is first bent at the waist and then straightened.

• 3 Statistics 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.

verb (jackknifes, jackknifing, jackknifed)

• move one’s body into a bent or doubled-up position:she jackknifed into a sitting position
• (of an articulated vehicle) bend into a V-shape in an uncontrolled skidding movement: the accident happened when a lorry jackknifed
• (of a diver) perform a jackknife.