USN is an acronym that stands for United States Navy. However, there are several synonyms that can be used in place of USN, depending on the context in which it is used. Some of the synonyms for USN are naval forces, seagoing service, United States naval forces, the navy, and seaborne military. You may also hear terms like naval warfare, naval defense, and naval operations used in place of USN. These synonyms can come in handy when writing papers or articles about the United States Navy, as they can be used to avoid repetition and keep the text interesting and engaging.