A colorless gas (O3) soluble in alkalis and cold water; a strong oxidizing agent; can be produced by electric discharge in oxygen or by the action of ultraviolet radiation on oxygen in the stratosphere (where it acts as a screen for ultraviolet radiation) WordNet 3.0 & Open English WordNet

Ozone is an inorganic molecule with the chemical formula O3. Wikipedia

Molecule consisting of three oxygen atoms. Wikipedia Disambiguation

Chemical compound Wikidata

An allotropic form of oxygen containing three atoms in the molecule. It is a bluish gas, very active chemically, and a powerful oxidizing agent. Ozone is formed when oxygen or air is subjected to a silent electric discharge. It occurs in ordinary air in very small amounts only. OmegaWiki

An allotrope of oxygen (symbol O₃) having three atoms in the molecule instead of the usual two; it is a blue gas, generated from oxygen by electrical discharge. Wiktionary