1. Something passed between routines OR programs that enables the receiver to perfORm some operation a capability ticket ORopaque 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)