TLDR: I ended up using the the_post hook to add the definitions as the posts are setup. This of course costs another trip to the database for every post but dealing with the duplicate entries proved too difficult.
Extending the WP_Query Class caused more trouble than it was worth. But forFor those interested..., however, here's how I did itextended the WP_Post Class to roll the duplicate posts up into one. I
I suspect this approach is not recommended.