"Gyrene" is a slang term used to refer to a United States Marine, and there are many synonyms for this word. Some of the commonly used synonyms are jarhead, devil dog, leatherneck, and grunt. These words are often used by the military personnel themselves, or among civilians who are close to the military community. Although they all refer to the same group of individuals, they carry different connotations and meanings. Some synonyms are used in a positive sense, while others may have negative connotations, depending on the context in which they are used. Ultimately, these words serve as a way to identify and group this respected and revered branch of the military.