Verb (used without object) : The prizefighter jackknifed and fell when he was hit in the stomach.    From Dictionary.com. 

Verb (used with object) : The blow jackknifed the prizefighter.    From Dictionary.com. 

There's multiple cars that have spun out, big rigs, several jackknifes.    From Wordnik.com.  [CNN Transcript Jan 17, 2007] Reference

And, for example, three months ago they took jackknifes off of their list.    From Wordnik.com.  [CNN Transcript Aug 13, 2006] Reference

I saw hundreds, maybe thousands, of holes left by jackknifes and razor clams, but no keyholes.    From Wordnik.com.  [Bottling day] Reference

You can clearly see how they are laid out in order from the head end (at the left) to the tail end (which extends to the right, and then jackknifes over the top).    From Wordnik.com.  [The Panda's Thumb: September 2006 Archives] Reference

And, in the most resonant strand here, a frazzled twentysomething widow named Lusa Maluf Landowski tries to make a go of her farm after her husband's truck jackknifes.    From Wordnik.com.  [Getting Back To Nature] Reference

News is Breaking: Camper jackknifes; 7-mile backup along Route 81 north.    From Wordnik.com.  [News Channel 9: Local News] Reference

Hundreds of motorists in NY stranded overnight after semi jackknifes, snow buries idling cars.    From Wordnik.com.  [StarTribune.com rss feed] Reference

The driver loses control of the semi as it jackknifes and falls onto it's side and slides into the police car and the car the officer is ticketing.    From Wordnik.com.  [Latest Articles] Reference

A combination of rapid, heavy snowfall; multiple tractor-trailer jackknifes; and a power outage that knocked out a primary radio tower for the Turnpike all conspired to leave southbound travelers stranded on the Turnpike, they said.    From Wordnik.com.  [The Charleston Gazette -] Reference

A truck jackknifes off an “arrow straight country road” near Kearney, Nebr., in Powers’s ninth novel, becoming the catalyst for a painstakingly rendered minuet of self-reckoning.    From Wordnik.com.  [While We’re on the Subject of Infobahn Novelists : Edward Champion’s Reluctant Habits] Reference

Its body jackknifes in his hand.    From Wordnik.com.  [The Shell Collector : Stories] Reference

Semi jackknifes; I-75 backed up for miles.    From Wordnik.com.  [Local News from The Gainesville Sun] Reference

Horses safe after trailer jackknifes on I-84.    From Wordnik.com.  [News from www.rep-am.com] Reference

"title":"Hundreds of motorists stranded in snowstorm","description":"In western New York, a truck jackknifes and then snow buries motorists stuck in the backup.    From Wordnik.com.  [Redskins Insider Podcast -- The Washington Post] Reference