Hey Suzanne

Thanks for posting in the Lucid Community! Although there is not a native hover feature you could add a note to the entities that you would like to have a definition. To add a note right click on the table you would like to add a note to and select Add Note. You will then see a small notification at the top right of the entity that when clicked will show the content you decide to type. 

Hope this helps--if not feel free to comment back and we can continue to troubleshoot. Cheers!