There are in fact several English words containing -uu-, all of Latin origin. The most common are vacuum and continuum; the less common ones are menstruum, residuum, triduum, and the distinctly rare duumvir and duumvirate.
If, after browsing the FAQs, you still can't find the answer to your question then submit your query to the AskOxford Language Query team.
Printer Friendly Version
