7
Having deposited your turd in the toilet, you look back to discover that its poking out of the water, too long and solid to go round the u-bend.
I had to go and fetch a stick so I could break up the jack-knife and flush the little devil.
by n_m April 01, 2004
Get a jack-knife mug for your friend Julia.
8
another term for a rude person, synonymous with asshole, jerk, dick, bastard

a way to curse without offending your grandparents
1) Dude, look at that jack-knife over there, what a douche!!
2) Quit being a jack-knife!!
by Jigga JMO September 07, 2006
Get the jack-knife neck gaiter and mug.
9
A "Jackknife" is made by dropping a shot of Jack Daniels into a glass of Corona, depth charge style.

Similar to a Jägerbomb.
Bar Guy 1: Just give me a beer
Bartender: And for your friend?
Bar Guy 2: Ill have a Jackknife, cause I'm a real man.
by Muhammed Ali Ganoo September 02, 2008
Get a Jackknife mug for your Facebook friend Georges.
10
A dive in which you jump into a pool , fold in your body with your hands & feet close to each other with the finger tips and toes pointing down, then unfolding bringing your feet to the air and keeping your hands where they are.
person 1 on diving board "HEY GUYS! CHECK OUT THIS JACK KNIFE IM GONNA DO IN THIS POOL!!"
person 2 from a far "YEAH DO IT!"
by Banzai Boy November 23, 2018
Get the Jack Knife neck gaiter and mug.
11
A knife that folds out of the handle!

You know you’re dead when that jackknife folds!
Me: *sees jackknife*
Stabber: *folds knife out of handle discreetly*
Me: *runs away*
by Stabberman420 March 31, 2020
Get a Jackknife mug for your brother-in-law Bob.
12
The action of pulling your pants down while driving, squatting above the seat, reaching your hand underneath your bottom, defecating into your hand, and then using the feces to smear your windshield. Done ritualistically for courting purposes.
The man decided to jackknife while driving on highway 99, in an attempt to enamor his lady friend.

There are people who jackknife to relieve stress during bumper-to-bumper traffic.
by English Professor with a PhD December 08, 2017
Get a Jackknife mug for your brother-in-law Paul.