Real Dictionary

ozone
Ozone is a colourless gas which is a form of oxygen. There is a layer of ozone high above the earth's surface.

ozone in American English
an unstable, pale-blue gas, O3, with a penetrating odor: it is an allotropic form of oxygen, formed usually by a silent electrical discharge in air, and is used as an oxidizing, deodorizing, and bleaching agent and in the purification of water
noun: a form of oxygen, O3, with a peculiar odor suggesting that of weak chlorine, produced when an electric spark or ultraviolet light is passed through air or oxygen. It is found in the atmosphere in minute quantities, esp. after a thunderstorm, is a powerful

ozone in British English
noun: a colourless gas with a chlorine-like odour, formed by an electric discharge in oxygen: a strong oxidizing agent, used in bleaching, sterilizing water, purifying air, etc. Formula: O3; density: 2.14 kg/m3; melting pt: –192°C; boiling pt: –110.51°C