jackknife
jackknife Lexical Profile
jackknife Game Scores & Validity
• noun
A large pocketknife with a blade or blades that fold into the handle.
"The camper used a sturdy jackknife to whittle kindling for the evening fire."
A dive in which the diver bends in midair to touch the toes with the hands while keeping the legs straight, then straightens the body before entering the water headfirst.
"She executed a graceful jackknife from the three-meter springboard."
In statistics, a resampling technique that estimates the bias and variance of a parameter by systematically leaving out one observation at a time from a dataset.
"The researchers applied the jackknife to assess the stability of their regression model."
• verb
To fold or bend at an acute angle like the blade of a folding knife (especially of an articulated vehicle whose trailer swings around toward the cab during a skid).
"The tractor-trailer jackknifed on the icy highway, blocking two lanes of traffic."
To bend the body sharply at the waist in midair or when springing upward, as when performing a dive or athletic maneuver.
"The gymnast jackknifed over the vault with impressive height and control."
• Nearby Words
Word Origin & Etymology
Attested in the early 18th century, the word combines 'Jack' (often used in compounds to denote a common utility tool) and 'knife', though an older Scottish dialect variant 'jockteleg' derives from the name of 16th-century French cutler Jacques de Liège.