As I was reading through some of the s9y.org older forum items, I saw an older plugin[?]request for a glossary. Specifically, for every occurance of a word, like xyzzy, the plugin would autoformat it and provide a popup with the definition.
I figure that this could be pretty easily implemented, so am starting to look at options. Currently, my choices are a wikipedia or wictionary lookup, or maintaining definitions locally. Because either of the lookups would be pretty intensive at load time, they would have to be done in the backend, somehow.
I'm currently thinking of having them maintained as a simple text list of word/definition pairs, but there might be a way to look things up in either wikipedia or wictionary at save time, so they can be stored...
In terms of display, this can be done by defining a class and using the title attribute of a span to make a tooltip:
<SPAN title=" description here " class="popup">text</SPAN>
Which would get rendered with a popup in Internet Explorer and Firefox like this text here.