jackknife

noun jack·knife \ ˈjak-ˌnīf \

Definition of jackknife

1 :a large strong pocketknife

2 :a dive executed headfirst in which the diver bends from the waist and touches the ankles while holding the knees unbent and then straightens out

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Recent Examples of jackknife from the Web

No weapon was found on Napier, although investigators discovered a jackknife and an ice pick-type tool stuck into the wall of the garage, not far from where Napier was first confronted.

— jeff mcdonald, sandiegouniontribune.com, "Oversight panel says deputies gave 3 different stories in 2014 fatal shooting," 27 July 2017
Meanwhile, deadbugs, jackknives, ab-wheel rollouts, and boat pose variations will hit both portions.

— k. aleisha fetters, SELF, "Why It’s So Hard to Work Your Lower Abs," 4 July 2017
One photograph captured the image of a towheaded boy of about 3, stripping bark off a stick with a jackknife.

— alice gregory, New York Times, "Running Free in Germany’s Outdoor Preschools," 18 May 2017
T. Christianson (@MSPPIO_SOUTH) January 10, 2017 SE MN very windy and fresh snow cause semis to jackknife.

— tad vezner, Twin Cities, "More snow makes for another lousy commute," 10 Jan. 2017

These example sentences are selected automatically from various online news sources to reflect current usage of the word 'jackknife.' Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.

First Known Use of jackknife

1711

jackknife

verb

Definition of jackknife

intransitive verb

1 :to double up like a jackknife

jackknifed into a seat beside me, folding up his six feet eight
—Lady Bird Johnson

2 :to turn and form an angle of 90 degrees or less with each other —used especially of a tractor-trailer combination

transitive verb

1 :to cause to double up like a jackknife

2 :to cut with a jackknife

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Examples of jackknife in a Sentence

The truck jackknifed on the icy road.

Recent Examples of jackknife from the Web

Swiveling, jackknifing, raising her arms, and then crumpling over, Dunst has as much intensity as a Martha Graham dancer.

— amy larocca, The Cut, "Queen of the Wood Nymphs," 8 Aug. 2017