Which term refers to the ceiling on a naval ship?

The term that refers to the ceiling on a naval ship is "overhead." In naval terminology, the "overhead" describes the structure that is located above the deck level. This term is commonly used aboard ships to identify the area above the crew's head, encapsulating various systems and elements of the ship's infrastructure.

Using the term "overhead" helps to maintain consistency and clarity in communication among sailors, especially when giving directions or performing operations. The other terms provided do not accurately represent the concept of a ceiling on a naval ship. For instance, "ceiling deck" is not a standard term in naval lexicon; "testudo" refers to a shield formation used by ancient Romans and has no relevance to naval construction; and "hutch" typically refers to a type of storage or enclosure, neither of which serves to accurately describe the overhead space in a ship.