We all know our tag wiki needs work. I've been thinking this over and I think one reason why it is the way it's now is that we do so little with it. When you ask a new question you get to see this
when you start typing a tag name. So you pick one and move on. No wiki. I very much doubt that other users who visit the question will click the tag to read the wiki. Correction: I'm absolutely sure they don't. So when do we see the wiki? Never.
What if we would use the tags more? Like in-lining them in the body of a question or answer, like you would have hyperlinks in a Wikipedia article? I would show them different from common hyperlinks, though I think the boxed format disrupts the text flow. I would rather think of a dashed or even wavy underline.
I think we can promote the tag wiki to a genuine lexicon this way. We may get more clicks to the wiki and maybe we'll get more summaries written.
One caveat: there's the risk of lexicon link overload, that a user would insert a link for every term they use in the text. I've seen articles on Wikipedia where they mention the cost of something, with the "$" hyperlinking to the WP article on the dollar.
So, a lexicon, what do you guyz/galz think?