A little while back, the Cambridge (MA) LessWrong group discussed building a site called Braintropes, specifically focused around defining rationality jargon; essentially, something like the LessWrong Wiki but optimized for causing tabsplosions. The idea was that a large vocabulary of concepts is an incredibly powerful thinking tool, and increasing the size of vocabulary the community could use would make it more effective. That project failed to take off (because of the amount of content-creation work required), but I still think it'd be valuable, and I'd be quite happy if Arbital ended up filling that role.
In practice, most jargon enters the lexicon through a canonical blog post which shares its name. If this is optimized for being a reference (rather than a tabsploder), Terms should in most cases consist of a link and an optional summary. It would also help if the creation of links to Terms was partially automated.