noun (plural jackknives)
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.
- 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.
- 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.
- 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.
- 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.
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.
- 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.
- 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.
verb (jackknifed, jackknifing)[with object]
1Move (one’s body) into a bent or doubled-up position: the Major jackknifed his thin body at the waist [no object]: she jackknifed into a sitting position
More example sentences
- With a harsh indrawn breath, I jackknife to a sitting position.
- Students then jackknife their legs even closer to their bodies to the rhythm of a driving beat.
- Jimjim's body suddenly jackknifed, wrenching his figure to the side.
1.1 [no object] (Of an articulated vehicle) bend into a V-shape in an uncontrolled skidding movement.
- Mr William tried to slow down by pumping his brakes but the vehicle jackknifed in the road while trying to avoid Mr Utting.
- The snow came down in handfuls and cars jackknifed to the left and right of us as we drove east on unplowed streets.
- A double-semi had jackknifed, neatly shutting down four lanes.
1.2 [no object] (Of a diver) perform a jackknife.
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