jack·knife / ˈjakˌnīf/ • n. (pl. -knives) 1. a 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.• v. (-knifed, -knif·ing) [tr.] move (one's body) into a bent or doubled-up position: the Major jackknifed his thin body at the waist | [intr.] she jackknifed into a sitting position. ∎  [intr.] (of an articulated vehicle) bend into a V-shape in an uncontrolled skidding movement. ∎  [intr.] (of a diver) perform a jackknife.

jackknife A statistical technique in which, given a data set with n observations, the analysis is recalculated n times omitting each observation in turn (removed with a “jackknife”). The mean and variance of the estimated parameters in the model may be compared with those obtained from the full set. The method is related to statistical bootstrap estimation.