An air pollution control device using the exhaust system of cars. The converter helps complete combustion of any fuel that was not burned in the engine and reduce the presence of other harmful emission concentrations. The converter changes the unburned hydrocarbons and carbon monoxide in the exhaust into carbon dioxide and water vapor. The converter use chemical catalysis to create this change. [Fleisher, Paul. Ecology A to Z. Dillon Press, New York. 1994. p. 38.]
Catalytic destruction of ozone -
Cl2 + hv -> 2Cl* (this reation produces chlorine radicals)
Cl* + O3 -> ClO* + O2 (chlorine reacts with ozone to form chlorine monoxide)
O3 + hv -> O* + O2 (ozone is also photolyzed to produce atomic oxygen)
ClO* + O* -> Cl* + O2 (chlorine radicals are reformed)
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NET: 2O3 -> 3O2 (the result is conversion of ozone to molecular oxygen)

This definition is in context to Atmospheric Chemistry. See more contextual defintions for Catalytic Converter.