Knuckle-Butter Share definition Flag The peanut butter that ends up on your knuckles when your knife/spoon is shorter than the jar. This tiny plastic knife is no match against that big ass jar of Jiff. Got me covered in the knuckle-butter... Knuckle-Butter by Grandmaster Dave November 27, 2017 0 0 Get merch Get the Knuckle-Butter mug. Buy Now — $32.95 See more merch