knifedildo Share definition Flag A device in which one end is a large, penis-shaped dildo, while the other end is a 7-inch steel blade. Girl: "I haven't been able to walk since I used the knifedildo." Guy: "Which end did you use?!" knifedildo by Derek Longass February 11, 2010 0 0 Get merch Get the knifedildo mug. Buy Now — $32.95 See more merch