<p><strong>Noun</strong></p><ul><li>Chemistry: Any substance capable of reducing the speed of a given reaction.</li><li>Something that impedes; an obstacle or hindrance.</li></ul><p><strong>Adjective</strong></p><ul><li>Retarding or tending to retard (usually used in combination): fire-retardant construction materials.</li></ul><p><strong>End of Response</strong></p>