jackknife

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jackknife

1. a knife with the blade pivoted to fold into a recess in the handle
2. a former name for a type of dive in which the diver bends at the waist in midair, with his legs straight and his hands touching his feet, finally straightening out and entering the water headfirst: forward pike dive
References in classic literature ?
Which would have advanced the most at the end of a month -- the boy who had made his own jackknife from the ore which he had dug and smelted, reading as much as would be necessary for this -- or the boy who had attended the lectures on metallurgy at the Institute in the meanwhile, and had received a Rodgers' penknife from his father?
A semi jackknifes on the freeway, backing traffic up for miles and inspiring everyone to react amusingly: Dad (Bryan Cranston) reflects, in a pathetically maudlin fashion, on his own mortality.
The newly formed molecule, at first joined to both arms of the frame, jackknifes upward as the amino adenosine severs its hydrogen bonds with the frame and snaps in place over the ester.