Well, I finally found the time to get back to this glossary thing. With the help of the Highlight Search Queries plugin[?]by Tom Sommer, I was able to get some happy pattern matching for a glossary plugin.
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.