The crossword solution for the term (ON) SET is GEL, which is a three letter word. GEL is a thick, semi-solid substance that is used in a variety of products, such as cosmetics, food, and pharmaceuticals. It is also used to hold hair in place, as well as to provide a protective coating for skin and nails. GEL is made up of a combination of water and a polymer, such as polyacrylamide or polyvinyl alcohol.