High-overhead baroque code-intenSIve featureful, but costly. Especially used of communication protocols, language deSIgns, and any sort of implementation in which maximum generality and/or ease of implementation has been pushed at the expense of mundane conSIderations such as speed, memory use and startup time. Emacs is a heavyweight editor X is an *extremely* heavyweight window system. This term isn' t pejorative, but one hacker' s heavyweight is another' s elephantine and a third' s monstroSIty. OppoSIte: "lightweight". Usage: now borders on technical especially in the compound "heavyweight process". (1994-12-22)