The two crossword solutions for the term 'gun powder ingredient' are SULFUR and niter. SULFUR is a non-metallic chemical element with the atomic number 16 and symbol S. It is an abundant, multivalent non-metal. Niter, also known as potassium nitrate, is a naturally occurring mineral composed of potassium, nitrogen, and oxygen. It is used in gunpowder and other explosives, as well as fertilizers and food preservatives.