jackknife
noun
jack·knife
| \ ˈjak-ˌnīf
\
\
Definition of jackknife
(Entry 1 of 2)
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
verb
jackknifed;
jackknifing;
jackknifes
Definition of jackknife (Entry 2 of 2)
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
Examples of jackknife in a Sentence
Verb
The truck jackknifed on the icy road.Recent Examples on the Web: Noun
The fourth vehicle then ran into a semi-truck, which caused the semi to jackknife and slam into the center median. — Dallas News, "Wrong-way driver in deadly Duncanville crash gets life sentence," 23 Aug. 2019 The suspect stabbed the victim with a jackknife at the Temple Street YWCA at about 6:40 p.m., Cambridge police spokesman Jeremy Warnick said in an e-mail. — Adam Sennott, BostonGlobe.com, "Cambridge police search for suspect in fitness class stabbing," 21 Aug. 2019 In one of his average workout classes, Curtis Adams will lead his group through a series of exercises, including jogging, jackknives and cardio boxing. — Olivia Lloyd, sun-sentinel.com, "Exercise instructor redefines fitness for seniors," 1 Aug. 2019 Police found Flick’s 3 ½ inch jackknife in the living room. — Wendy Grossman Kantor, PEOPLE.com, "What to Know About Albert Flick, the 77-Year-Old Murderer Deemed 'Too Old' to Be Violent," 19 July 2019 In his video, Kirsch walks viewers through hanging knee raises, a medicine ball spiderman, jackknives, and a medicine ball slam. — SELF, "A Quick Core-Burning Workout From Jennifer Lopez's Trainer," 26 Oct. 2018 All new power ottomans and jackknife seats will complement two-tone high-end cabinetry, and plush diamond-stiched seating. — Megan Barber, Curbed, "This limited edition Airstream touring coach goes all in on luxury," 5 Oct. 2018 John Paul Vitruk, 64, was driving south on Highway 169 with a loaded U-HAUL trailer attached to his pickup truck when the truck hit an icy area on the road, causing the trailer to jackknife, said Lee County Coroner Bill Harris. — Anna Beahm, AL.com, "Auburn man killed after wreck on icy highway in Lee County," 19 Jan. 2018 The extremely limited-run beer is limited to 200 bottles, sold as survival kits that include a solar blanket, paracord, and Swiss Army jackknife. — Matt Allyn, Popular Mechanics, "Creating the Perfect Beer for the End of the World," 5 Jan. 2018Recent Examples on the Web: Verb
The new model meets new, stronger crash-worthiness standards and is designed not to jackknife — guarding against the kind of derailment that killed eight people when Amtrak 188 took a turn too fast near Philadelphia in 2015. — CBS News, "Inside Amtrak's next-generation Acela train: "Wi-Fi, craft beers and reliable schedules"," 11 June 2019 Oftentimes, jackknifing is a result of improper braking, poor road conditions or equipment failure. — Kimberly Rapanut, azcentral, "Loop 101 WB at Hayden closed in Scottsdale after semitruck jackknifes," 11 June 2018 The truck subsequently jackknifed and slid across all lanes of traffic, leading to the shutdown of the westbound side for a full eight hours. — Carol Cormaci, latimes.com, "La Cañada History: Viper collides with big rig, shuts down 210 Freeway for 8 hours," 9 Apr. 2018 On Twitter, State Police said tractor-trailers were jackknifed at various locations in central Massachusetts. — Laney Ruckstuhl And Elise Takahama, BostonGlobe.com, "Treacherous roadways cause at least 9 tractor-trailer crashes," 13 Mar. 2018 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. 2017These 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.
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More Definitions for jackknife
jackknife
noun
English Language Learners Definition of jackknife
(Entry 1 of 2)
: a small knife that has a folding blade
: a dive in which you bend from the waist and touch your ankles and then straighten out
jackknife
verbEnglish Language Learners Definition of jackknife (Entry 2 of 2)
: to bend in the middle like a folding jackknife
especially, of a large truck
: to have the back part slide out of control toward the front part
See the full definition for jackknife in the English Language Learners Dictionary
jackknife
noun
jack·knife
| \ ˈjak-ˌnīf
\
\
plural jackknives\ -ˌnīvz \
Kids Definition of jackknife
(Entry 1 of 2)
: a knife that has a folding blade or blades and can be put in a pocket
jackknife
verb
jackknifed;
jackknifing
Kids Definition of jackknife (Entry 2 of 2)
: to double up like a jackknife
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