noun
: a soluble crystalline salt KNO 3 with a cooling saline taste that occurs as a product of nitrification in most arable soils especially in hot dry countries where it is extracted by leaching but that is usually made by reaction of potassium chloride and sodium nitrate, that decomposes on strong heating into potassium nitrite KNO 2 and oxygen, and that is used chiefly in making black powder, matches, and fireworks and in curing meat — called also niter, saltpeter