Recently in a U.S. History class, my professor stated that the Lusitania was not only secretly carrying munitions, but also armed with deck guns. I know the British Navy used Q-ships (merchant vessels with hidden guns), but haven't been able to find any source stating the Lusitania was one of these ships.
Yes, it was unarmed. The ship had mounts for six-inch deck guns, but they were never mounted.
I wrote about the Lusitania before, if it's of interest.