Well, I like the idea of members being able to search, if it turns our you have a huge database of terms, this would be ideal. I think allowing those to view all terms would be a nice idea, but if you are going to implement the search feature, there is not much of a reason to implement a "View All", imo.
In regards to allowing "Term Submissions" I think that would be great, but they would have to be moderated in a way, you would not want loads of trash filling up your glossary for you to later have to delete.
Maybe have a form where only members can fill it out, once they fill it out, it is directly sent to the webmaster/administrator with the term and it's difinition. Once the admin/webmaster reviews it, he/she can then add it to the database (this would take away the time it takes to moderate them, instead, it directly goes to the admin/webmaster).
Just my thoughts.

- Still a nice hack