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)