Jar Head is a term used to refer to a member of the United States Marine Corps. The term is derived from the distinctive headgear worn by Marines, which is known as a 'COVER' or 'HAT'. The term LID is an acronym for the Marine Corps' official headgear, which stands for 'Leather Infantryman's COVER'. The Leather Infantryman's COVER is a black leather HAT with a flat brim and a chin strap. It is worn by all Marines in uniform and is a symbol of their service.