What is the term used to describe an armed naval vessel?

The term "man of war" historically refers to a powerful warship primarily used during the Age of Sail, capable of carrying both weapons and a complement of sailors for naval combat. This designation originated in the 16th century and was primarily used to describe ships designed specifically for warfare rather than commerce.

"Man of war" captures a significant aspect of naval history, symbolizing the might of a nation's naval forces and their ability to project power at sea. While the other options, such as "warship," "cruiser," and "frigate," also describe armed naval vessels, they represent different classifications or types within the broader context of naval warfare. For instance, a warship is a more general term that encompasses all ships designed for combat, while cruisers and frigates are specific types of warships with distinct roles and capabilities.

Thus, "man of war" is correctly identified as a term with historical significance and specificity in the context of naval vessels designed for armed conflict.