noun, plural jack·knives.
verb (used without object), jack·knifed, jack·knif·ing.
verb (used with object), jack·knifed, jack·knif·ing.
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Example sentences from the Web for jackknife
He had his jack-knife out, and was already slashing carefully the shirt of Happy Jack, that he might inspect the wound.Flying U Ranch|B. M. Bower
Examining a tree, he took out his jack-knife and went to work near the ground, and he soon showed why the tree was not doing well.The Apple|Various
A plug of tobacco also went the round, each whittling off a piece to suit himself, with his jack-knife.An Undivided Union|Oliver Optic
He pulled out his jack-knife and pushed it into the fog, clean to the handle.Jim Spurling, Fisherman|Albert Walter Tolman
It was suggested that he go out on a sand lot and take up a jack-knife collection from the boys playing ball.The Galloping Ghost|Roy J. Snell