Duc Guy Share definition Flag Person who thinks he has a large penis. But in reality it is very small. Most of the time (Duc Guy) is gay. Duc Guy: My dick is huge! Look at it! Everyone: BhahahhAHAHAahhah! its so tiny! Duc Guy by Facts. December 17, 2008 0 0 Get merch Get the Duc Guy mug. Buy Now — $32.95 See more merch