Easter egg

( n.)
   [from the custom of the Easter Egg hunt observed in the U.S. and many
   parts of Europe]

   1.  A  message  hidden  in  the  object  code of a program as a joke,
   intended to be found by persons disassembling or browsing the code.

   2. A message, graphic, or sound effect emitted by a program (or, on a
   PC, the BIOS ROM) in response to some undocumented set of commands or
   keystrokes,  intended  as  a  joke or to display program credits. One
   well-known  early Easter egg found in a couple of OSes caused them to
   respond  to  the  command  make  love  with  not  war?. Many personal
   computers  have  much  more  elaborate  eggs hidden in ROM, including
   lists  of  the developers' names, political exhortations, snatches of
   music,  and  (in  one case) graphics images of the entire development
   team.
[glossary]
[Reference(s) to this entry by made by: {xyzzy}]