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.
A code used by polcie departments and 911 dispatchers to signal the use of any kind of drug
"We have a fight, it may be code 18 related" "A group of people outside smoking code 18"