Why not use some Javascript and have a "pop-up" when someone clicks on the word in the text?
I use a script that I got from dynamicdrive.com and it works very well and, YES, the search engine can index the content because the content is a <div> that is visible when someone clicks on the link. So whenever you refer to a technical word or phrase, simply make it a link that will pop up the meaning of that word or phrase. Makes it very convenient for the site visitor.
You can find the script I use at
Dynamic Drive DHTML Scripts- Drop down/ Overlapping Content script