jackknife

1 of 2

noun

jack·​knife ˈjak-ˌnīf How to pronounce jackknife (audio)
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

jackknife

2 of 2

verb

jackknifed; jackknifing; jackknifes

intransitive verb

1
: to double up like a jackknife
jackknifed into a seat beside me, folding up his six feet eightLady 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

Examples of jackknife in a Sentence

Verb The truck jackknifed on the icy road.
Recent Examples on the Web
Noun
And the name of the game is squats: Pistol squats, goblet squats with weight, and jackknife crunches are all part of the usual regimen for Naomi. Jacqueline Tempera, Women's Health, 28 Apr. 2023 Nissan says the SUVs have jackknife folding keys that may not stay fully open. CBS News, 28 Feb. 2023
Verb
What to know 1:50 p.m.: All WB lanes on Watterson Expressway at Shelbyville Road closed after semi-truck crash All westbound lanes near the 20-mile marker on Interstate 264 are closed after a tractor trailer jackknifed on the roadway Friday afternoon. Marina Johnson, The Courier-Journal, 25 Jan. 2024 The big rig jackknifed approximately 20 feet off the roadway and down an embankment, according to the CHP. Rick Hurd, The Mercury News, 18 July 2024 See all Example Sentences for jackknife 

These examples are programmatically compiled from various online sources to illustrate current usage of the word 'jackknife.' Any opinions expressed in the examples do not represent those of Merriam-Webster or its editors. Send us feedback about these examples.

Word History

First Known Use

Noun

1683, in the meaning defined at sense 1

Verb

1886, in the meaning defined at intransitive sense 2

Time Traveler
The first known use of jackknife was in 1683

Dictionary Entries Near jackknife

Cite this Entry

“Jackknife.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/jackknife. Accessed 8 Oct. 2024.

Kids Definition

jackknife

1 of 2 noun
jack·​knife ˈjak-ˌnīf How to pronounce jackknife (audio)
1
: a large strong pocketknife
2
: a dive in which the diver bends from the waist and touches the ankles before straightening out

jackknife

2 of 2 verb
: to double up like a jackknife
the trailer truck jackknifed
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