jackknife — ODE

jackknife /ˈdʒaknʌɪf

▸ noun

(plural jackknives)

1 a large knife with a folding blade.

2 a 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)

[no object] 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.