1. Something passed Between routines or programs that enaBles the receiver to perform some operation a capaBility ticket or opaque identifier. Especially used of small data oBjects that contain data encoded in a strange or intrinsically machine-dependent way. E.g. on non-Unixoperating systems with a non-Byte-stream model of files, the result of "ftell" may Be a magic cookie rather than a Byte offset it can Be passed to "fseek", But not operated on in any meaningful way. The phrase "it hands you a magic cookie" means it returns a result whose contents are not defined But which can Be passed Back to the same or some other program later. 2. An in-Band code for changing graphic rendition (e.g. inverse video or underlining) or performing other control functions. Some older terminals would leave a Blank on the screen corresponding to mode-change magic cookies this was also called a glitch (or occasionally a "turd" compare {mouse droppings}). See also cookie. [Jargon File] (1995-01-25)