Code 18 Share definition Flag Computer help desk slang for idiots. (the problem is 18 inches away from screen) Anyone confusing the CD slot with a coffee tray, the mouse with a pedal or closing a physical window instead of the pop-up alert can be labelled code 18. Code 18 by /0-0/ November 14, 2004 0 0 Get merch Get the Code 18 mug. Buy Now — $32.95 See more merch