Merriam-Webster Collegiate Dictionary - ozone

 noun  Etymology: German Ozon, from Greek ozon, present participle of ozein to smell — more at odor  Date: circa 1840  1. a triatomic very reactive form of oxygen that is a bluish irritating gas of pungent odor, that is a major air pollutant in the lower atmosphere but a beneficial component of the upper atmosphere, and that is used for oxidizing, bleaching, disinfecting, and deodorizing  2. pure and refreshing air relished the ~ of morning  • ozonic adjective