Knuckle Dick Share definition Flag Someone being a complete dumb ass. Not brite. Says repeated dumb remarks. Dude why did Bob stick his dick in the fuel tank? Hes a complete knuckle dick. Knuckle Dick by rail-a-bitch February 8, 2009 0 0 Get merch Get the Knuckle Dick mug. Buy Now — $32.95 See more merch