1. A program used primarily to create, manipulate, modify, or analyse other programs, such as a compiler or an editor or a cross-referencing program. Opposite: app, operating system. 2. A Unixapplication program with a simple, "transparent" (typically text-stream) interface designed specifically to be used in programmed combination with other tools (see filter, plumbing). 3. (MIT: general to students there) To work to study (connotes tedium). The TMRC Dictionary defined this as "to set one' s brain to the grindstone". See hack. 4. (MIT) A student who studies too much and hacks too little. MIT' s student humour magazine rejoices in the name "Tool and Die". [Jargon File] (1996-12-12)