There are a few jQuery tooltip plug-ins (which is really what you're after). Personally I've been using jQuery Tooltip and am happy with it. I've used it to put some pretty complex content in a tooltip.
I don't fully understand the rest of your question. Do you want this to happen automatically? Is the table present on the page? Is server side code creating the definition bubbles?
Now jQuery Tooltip has a bodyHandler attribute where you can supply a callback (function) that'll define the content of the tooltip so that bit's fine. Do you want these links/tips automatically created though?
EDIT: Take a look at this highlight plug-in as well. Even if you don't use it you can copy the methods for finding text in your document and wrapping elements around them. Something like:
$(function() {
$("table.definitions th").each(function() {
var term = $(this).text();
var definition = $(this).nextSibling().text(); // assuming it's in a <td> in the same row
// find all occurrences of 'term' in relevant text block
// and wrap in <span class="term" title="definition">...</span>
});
});
Then optinoally use jQuery Tooltip to make a more modern tooltip out of that title.