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
Collins Discovery Encyclopedia, 1st edition © HarperCollins Publishers 2005
References in periodicals archive ?
"It looked to me like the collision made the trailer jack-knife and the digger on the back has landed right on top of the car."
He testified that as the forwards were forming for the scrum, Alex shouted the word 'jack-knife'.
The first lorry jack-knife happened on the A69 near Corbridge, Northumberland, on Saturday morning, and a further incident later that day on the A1(M) southbound at junction 60, in Country Durham.
As the group donned their waterproofs, an approaching heavy-goods vehicle lost control on the wet highway, causing its trailer to jack-knife at speed and collide with the stationary motorcycles, flinging one of the machines into Lee and killing him instantly.
Ainslie (JBAA 120(1), 2010 Feb) has answered questions which have been in my mind for 50 years, particularly on details of his 'jack-knife refractor'.
The resulting smash forced an articulated lorry to lock up, jack-knife and screech to a halt behind the bikes while cars had to swerve to avoid them.
The crash caused the tractor and its trailer to jack-knife and hurtle towards the barrier at a 45 degree angle.
What next, an amnesty on walking frames in case they jack-knife or on dentures, just in case you put them in back to front and eat yourself?
The motorway was shut between junction 16 at Barthomley and 18 at Holmes Chapel shortly after 5.30pm when two HGVs collided, causing one to jack-knife and block three lanes of the southbound carriageway.
Winston Rasaiah, an RAIB inspector and expert in train safety, said the train's black box recorded the exact time the train travelled at 95mph over the faulty points - 8.11pm and 49 seconds - and just 1.63 seconds later the first and second carriages began to jack-knife at 92mph.
75 Practical Ideas For Family and Friends from Cancer's Frontline, Grant, 44, tells how he cheered his mum up: "I got bored and went back to tormenting her - my personal favourite being secretly activating her hospital bed so that the head and legs both lifted to put her in an amusing jack-knife position."