/spās kə-ˈdet kē-bȯrd/
n. The Knight keyboard, a now-legendary device used on MIT LISP machines, which inspired several still-current jargon terms and influenced the design of EMACS. It was inspired by the Stanford keyboard and equipped with no fewer than *seven* shift keys: four keys for bucky bits ('control', 'meta', 'hyper', and 'super') and three like regular shift keys, called 'shift', 'top', and 'front'. Many keys had three symbols on them: a letter and a symbol on the top, and a Greek letter on the front. For example, the 'L' key had an 'L' and a two-way arrow on the top, and the Greek letter lambda on the front. If you press this key with the right hand while playing an appropriate 'chord' with the left hand on the shift keys, you can get the following results:
L
lowercase l
shift-L
uppercase L
front-L
lowercase lambda
front-shift-L
uppercase lambda
top-L
two-way arrow (front and shift are ignored)
And of course each of these might also be typed with any combination of the control, meta, hyper, and super keys. On this keyboard, you could type over 8000 different characters! This allowed the user to type very complicated mathematical text, and also to have thousands of single-character commands at his disposal. Many hackers were actually willing to memorize the command meanings of that many characters if it reduced typing time (this attitude obviously shaped the interface of EMACS). Other hackers, however, thought having that many bucky bits was overkill, and objected that such a keyboard can require three or four hands to operate.
See bucky bits, cokebottle, double bucky, meta bit, quadruple bucky.