Leave the search field but lose the filter groups and instead offer a few hand-selected glossary terms that might be of interest to our audience. Maybe something like:
Some Good Words to Know
OR
We don't have to highlight any words or groupings of words. We could just have the search field.
(And for what it's worth, I still like the idea of having a simple list of all the glossary entries in one spot, in a "browse all" kind of way.)