/kohk'bot-l/ Any unusual character, particularly one you can't type because it isn't on your keyboard. MIT people used to complain about the "control-meta-cokebottle" commands at SAIL, and SAIL people complained about the "altmode-altmode-cokebottle" commands at MIT. After the demise of the space-cadet keyboard, "cokebottle" was used less, but was often used to describe weird or non-intuitive keystrokes.
The OSF/Motif window manager, "mwm" keystroke for switching to the default keybindings and behaviour is control-meta-bang. Since exclamation mark might be thought to look like a Coke bottle, Motif hackers referred to this keystroke as "cokebottle".
See also quadruple bucky.