Word can't really do that. (You probably got the idea from looking at a web
page, but Word isn't HTML.)
The closest you'll get is to surround the word or term with a bookmark, then
create a hyperlink pointing to the bookmark, and enter the definition as the
hyperlink's screentip. Unfortunately, the screentip will contain a bold
statement "Ctrl+Click to follow link" that you can't remove. You're also
limited to 255 characters in the definition.
Another possibility is to enter the definition as a comment, but this time
your name and the date/time you enter the comment will appear in the popup,
and your initials will appear in the text. On the plus side, the length of a
comment isn't limited.
--
Regards,
Jay Freedman
Microsoft Word MVP
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