Synthetic Jack Black 

The purest substance on Earth. Will take you from the decking to the beach in 3 seconds flat!

“Hey dude you got the *good stuff*?”
“Yeah dude. I got the *synthetic jack black”
“Ohhh yeah dude bowel cancer time!”

Synthetic Jack Black by Kidslayer69 January 12, 2020

Sam Jack

He is a 5'5 african american male who loves hi neighbour and wishes his female friend who begins with a G would live next to him.

He also likes boys

Sam jack is mullet man

Sam Jack by Hoesmadcuh February 28, 2022

The Summer Jack 

A shot of Jack Daniels whiskey brought to 95 degrees farenheit, shot back, and spit all over the hottest girl in the bar.

Yo, that muthafucka just summer jacked becky. What a hot ass duche. Damn I can't believe he did The Summer Jack to her.

The Summer Jack by Pseudopluto November 19, 2014

Pull a Jack 

The act of doing something that goes against all mortal logic and basic understanding aswell as denying the laws of physics.
This can take form in many different ways but most often is defined when great risk accompanies the action.
For example - Pinging an entire Discord with the Risk of an Asian superior overlord erasing the "Jack's" existence.

A: @everyone
B: Could you not Pull a Jack

Pull a Jack by TheLenTM October 18, 2019

dirty jack 

When during sex the man is as stupid as simple jack and just keeps screaming you m-m-m-m-m-m make me happy and the girl just says you have a fine brain jack!

Guy: you m-m-m-m make me happy

Girl: ohhh you dirty jack

dirty jack by Havemenot December 21, 2013

Padded Jack 

Item of clothing worn on the medieval battlefields. Comprises 42 layers of wool and linen, soaked in either vinegar, salt water, wine or urine to make them stiff and tough to break through. Often either tied or buckled at the front, hence the modern word "jacket". Mostly foot soldiers and Billmen would wear them, as they were the poorer ranks and would not neccessarily own plate armour.

See above

Padded Jack by Taz June 2, 2004

Cactus Jack

There are several definitions floating around out there - but this is an original scenario and should be considered an authentic Cactus Jack henceforth -
If lonely in the desert, take a small cactus and carefully remove all needles. Insert a knife in the bottom and hollow out the pulp. You should now have a flap of cactus skin with a nicely lubricated, aloey, gooey lining. Carefully insert two fingers and feel around the inside looking for any "ingrown needles". Once satisfied that your cactus meets all safety requirements, you may proceed to have sex with it. Afterwards, rinse and repeat as desired. The flap will fold easily and can be kept discreetly in your pocket.

When Casey was doing infantry training out in the desert, I heard he got lonely in his fighting hole and made himself up a nice little Cactus Jack for company.

Cactus Jack by Daddy Ruxpin November 9, 2010