One of the mysteries of the English language finally explained.
1A knife with a folding blade.
- ‘Adam had chosen a jackknife rather than a fixed blade.’
- ‘With a jackknife, he whittled a point on a thin green stick pulled from a maple branch.’
- ‘The shorter girl snarled her frustration and lunged after him with her jackknife, tearing a horizontal gash in his right pant leg.’
- ‘I ducked down in onto my hands and knees, and right before my eyes, I saw the jackknife that Todd was carrying discarded on the ground, it was tremendously shiny, and glittered in the company of a red handle.’
- ‘Pen clips, protractors, and jackknives have left hacked shapes to tell people how dull it all was when they sat here.’
2A dive in which the body is first bent at the waist and then straightened.
- ‘Westmount borough chairman Karin Marks, on the threat of non-residents coming en masse to do jackknives in the Westmount pool’
- ‘But still, I usually like to lounge about in a chaise lounge or something while everyone else is doing cannonballs and jackknives and freakish flips off the diving board.’
- ‘With his opponent flat in the center of the ring, Van Dam climbs to the top turnbuckle, springs across the ring crouching and extending his torso like a diver performing a jackknife.’
- ‘Though his past leaps of faith have had about as much grace as a jackknife into a leaf-covered pool, bringing Gibbs back has ‘reverse pike triple somersault’ written all over it.’
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.
- ‘To evaluate clade support, bootstrap and jackknife analyses were performed in PAUP * using a full heuristic search with 1000 replicates, simple addition sequence, and TBR branch-swapping.’
- ‘We used the jackknife version of cross-validation, where the training set consists of the complete network minus a single specified edge.’
- ‘Occasionally, low Bremer support is correlated with a high jackknife percentage, e.g., at the node separating the Wnt1 subfamily from the rest of the tree and at the base of the vertebrate Wnt 10 sequences.’
- ‘Bootstrap and jackknife analyses were performed under the MP criterion, with equal weights for all positions and two random additions of sequences for 200 replicate searches.’
- ‘Higher-order jackknife estimates lead to successively greater reductions in the bias of the estimates of N d, but at the cost of increasing sampling variance.’
1Move one's body into a bent or doubled-up position.no object ‘she jackknifed into a sitting position’‘the Major jackknifed his thin body at the waist’
- ‘Jimjim's body suddenly jackknifed, wrenching his figure to the side.’
- ‘A spasm jackknifed me, crunched the air right out of me.’
- ‘Students then jackknife their legs even closer to their bodies to the rhythm of a driving beat.’
- ‘Galindo devilishly liked to stun nurses by jackknifing himself into a completely folded hospital bed.’
- ‘With a harsh indrawn breath, I jackknife to a sitting position.’
- 1.1no object (of an articulated vehicle) bend into a V-shape in an uncontrolled skidding movement.
- ‘The snow came down in handfuls and cars jackknifed to the left and right of us as we drove east on unplowed streets.’
- ‘Similarly, neither of the two units will be damaged if the trailer jackknifes with respect to the tractor.’
- ‘A double-semi had jackknifed, neatly shutting down four lanes.’
- ‘Mr William tried to slow down by pumping his brakes but the vehicle jackknifed in the road while trying to avoid Mr Utting.’
- ‘A semi-tractor and trailer jackknifed coming down the icy hill on Northeast North Woodinville Way at about the 14500 block.’
- 1.2no object (of a diver) perform a jackknife.
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