The term 'Informal D.C. Title' is a crossword solution that can be filled in with the 4-letter word 'PREZ'. This term is an informal title for the President of the United States, who is the head of the executive branch of the federal government. The President is elected by the people and serves as the commander-in-chief of the armed forces. The President is responsible for carrying out the laws of the United States and representing the nation in foreign affairs.