A term used to describe a US Marine. Although some believe the term is of recent origin (Gulf War), it has been around for a long time (at least since
World War II). It has
nothing to do with haircuts, hats or headshape. It refers to the Marines propensity to follow orders, regardless of consequences or personal safety. Because of their single-minded willingness to put their duty before themselves, Marines are said to have jarheads...hard on the outside and empty
on the inside. It is a good thing there are such men.