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English definition of “jackknife”

jackknife

verb [I] uk   /ˈdʒæk.naɪf/ us  
If a truck that has two parts jackknifes, one part moves around so far towards the other part that it cannot be driven: The oil tanker jackknifed after skidding on the ice.

jackknife

noun [C] uk   /ˈdʒæk.naɪf/ (plural jackknives) us  
a large knife with a blade that folds into the handle
(Definition of jackknife from the Cambridge Advanced Learners Dictionary & Thesaurus © Cambridge University Press)
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