The crossword solution for the term 'scuttle filler' is COAL, which is a four-letter word. COAL is a combustible black or brownish-black sedimentary rock, formed as rock strata called COAL seams. It is mostly carbon with variable amounts of other elements, such as hydrogen, sulfur, oxygen, and nitrogen. COAL is used as a fuel source for electricity generation, steel production, and other industrial purposes. It is also used in the production of coke, a fuel with few impurities and a high carbon content, which is used in smelting iron ore.