A chemical reaction in which a reaction intermediate or product enters into the reaction rate equation or functions as a catalyst. In such a reaction the observed rate of reaction can often develop into a very sudden and violent runaway reaction
Reference: adapted from IUPAC. Compendium of Chemical Terminology, 2nd ed. (the “Gold Book”). Compiled by A. D. McNaught and A. Wilkinson. Blackwell Scientific Publications, Oxford (1997).