This is usually used as a term that limits as someone's niceness that is used to show the limit of how nice someone can be. It says that there is always as nice as jack
by The OG of the OG September 2, 2016

man 1: jack branagan
man 2: malder
man 1: i gorilla glued my cock so its permenantly erect
man 2: jack branagan moment lul
man 2: malder
man 1: i gorilla glued my cock so its permenantly erect
man 2: jack branagan moment lul
by tommymald February 27, 2021

by Hot Dudes November 14, 2022

In a similar vein to photobombing, however instead of getting in the photo, you steal other peoples cheesy tourist shots by getting in the way of the photographer and taking the shot on your own camera.
by photojacker January 11, 2012

It goes with "doesn't know ..." You say it about somebody who doesn't know anything of any use at all, and when it is not enough to say "he doesn't know jack," and you are tired of "jack-shit."
The first four years of being an alderman, you don't know jack-bone! (Maze Jackson on his radio show)
by qariwa February 12, 2019

Darrell Strawberry stole Robert Downey Junior’s “Jack-Bag” in the 90’s, and used some of the Yay-O to do a bump out of Brooke Shields flat ass. #Classic
by SwingMan23 February 3, 2019

by Dani coola October 19, 2016
