I personally detest the hover widget, but it's probably a necessary evil. (We can probably get one that can be turned on/off in user preferences.)
Anyway, for now, see:
Glossary of abbreviations, acronyms & initialisms
Also "Glossary" is now a main navigation item. As with much else in life, it's a work in progress; consider it a start. Feel free to add more / make requests in that thread.