jack slattery Share definition Flag A dude who doesn't like it if you step on his "J"s and screams a lot. He also constantly starts fights and loses them. ex: GIMME BACK MY LUNCHBOX ex: he is such a Jack Slattery jack slattery by Mangernam October 5, 2013 0 0 Get merch Get the jack slattery mug. Buy Now — $32.95 See more merch