Definition of "pyrite"

(mineralogy) The common mineral iron disulfide (FeS2), of a pale brass-yellow color and brilliant metallic luster, crystallizing in the isometric system.  examples

(usually as a plural: pyrites) Any metallic-looking sulphide, such as the above, which is the most common.  examples

(solid state chemistry) (usually as a plural: pyrites) Any metal dichalcogenide that is isostructural to the common mineral.  examples