Source : Webster's Revised Unabridged Dictionary (1913)

Ozone \O"zone\, n. [Gr. 'o`zwn smelling, p. pr. of 'o`zein to
   smell. See {Odor}.] (Chem.)
   A colorless gaseous substance (O?) obtained (as by the silent
   discharge of electricity in oxygen) as an allotropic form of
   oxygen, containing three atoms in the molecule. It is a
   streng oxidizer, and probably exists in the air, though by he
   ordinary tests it is liable to be confused with certain other
   substances, as hydrogen dioxide, or certain oxides of
   nitrogen. It derives its name from its peculiar odor, which
   resembles that of weak chlorine.

Source : WordNet®

ozone
     n : 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)