pyrolysisPronunciation: /pʌɪˈrɒlɪsɪs/Definition of pyrolysis noun [mass noun] Chemistry decomposition brought about by high temperatures: steam pyrolysis of hydrocarbons [as modifier]:a pyrolysis furnaceDerivatives pyrolyticPronunciation: /pʌɪrəˈlɪtɪk/ adjective pyrolysis in other Oxford dictionaries Definition of pyrolysis in the US English dictionary