Mentum is a Latin word meaning momentum or impetus. It is often used in the context of legal proceedings, where it refers to the momentum of a case that has been established by a court ruling. The crossword solution for the term Mentum is CHIN, which is a four-letter word referring to the lower part of the face. This term is derived from the Latin word 'cingulum, ' which means girdle or belt. In this context, it can be interpreted as the force or impetus that drives a case forward.