The term SUB FILLER can be solved by the crossword solution MEATBALLS, which is a nine-letter word. Meatballs are a popular dish consisting of ground meat, usually beef or pork, that is formed into small balls and cooked in a sauce or broth. They are often served with pasta, rice, or vegetables. Meatballs are a staple of many cuisines around the world, including Italian, Swedish, and Chinese.