ozone

Concise Oxford English Dictionary © 2008 Oxford University Press:
ozone/ˈəʊzəʊn/

▶noun

• 1 an unstable, pungent, toxic form of oxygen with three atoms in its molecule, formed in electrical discharges or by ultraviolet light.

• 2 Brit. informal fresh invigorating air.

– derivatives
ozonic adjective.

– origin C19: from Ger. Ozon, from Gk ozein ‘to smell’.