1. [n]  a person of exceptional importance and reputation
2. [n]  a very large person; impressive in size or qualities
3. [n]  a boxer who weighs more than 195 pounds
4. [n]  a wrestler who weighs more than 214 pounds
5. [adj]  heaviest in a category or of a heavyweight category (more than 175 pounds for boxers); "a heavyweight boxer"

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".