The term 'MODERN PREFIX WITH FILL' is a crossword solution that consists of four letters: 'AUTO'. This prefix is derived from the Greek word 'AUTOS', which means 'SELF'. It is used to refer to something that is SELF-operating or SELF-governing. In modern usage, it is often used to describe technology that is automated or SELF-driving. Examples of this include autonomous vehicles, automated manufacturing processes, and artificial intelligence.