Origin of jackknife

1705–15, Americanism; jack1 (cf. jockteleg) + knife
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019

Examples from the Web for jack-knife

Historical Examples of jack-knife

  • Kit bought one of these for a jack-knife,—for a curiosity, of course.

    Left on Labrador

    Charles Asbury Stephens

  • Quin, doubled up like a jack-knife beside her, was drunk with ecstasy.


    Alice Hegan Rice

  • Yes, there was the cache I had made by splitting the pasteboard with my jack-knife.

    The Plum Tree

    David Graham Phillips

  • Then with his jack-knife he proceeded to investigate the inside.

    Tabitha's Vacation

    Ruth Alberta Brown

  • He had left his half-axe in camp, and when he felt in his pocket for his jack-knife it was not there.

    Forest Neighbors

    William Davenport Hulbert

British Dictionary definitions for jack-knife


noun plural -knives

a knife with the blade pivoted to fold into a recess in the handle
a former name for a type of dive in which the diver bends at the waist in midair, with his legs straight and his hands touching his feet, finally straightening out and entering the water headfirst: forward pike dive

verb (intr)

(of an articulated lorry) to go out of control in such a way that the trailer swings round at an angle to the cab
to make a jackknife dive
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Word Origin and History for jack-knife

also jackknife, large pocket knife, 1711, probably American English, "perh[aps] associated with some sense of JACK sb.1, but cf. jackleg knife" [OED]; see jack + knife (n.). Jackleg was a U.S. colloquial term of contempt from c.1850. On another theory, so called because it originally was associated with sailors. As a kind of swimming dive, from 1922. As a type of tractor-trailer accident, 1966. Both from the notion of folding, as the knife does.


1776, "to stab," from jack-knife (n.). Intransitive meaning "to fold or bend" the body is said to date from the time of the American Civil War. The truck accident verbal sense is from 1949. Related: Jackknifed; jackknifing.

Online Etymology Dictionary, © 2010 Douglas Harper