the speeding up or, sometimes, slowing down of the rate of a chemical reaction caused by the addition of some substance that does not undergo a permanent chemical change
See catalysis in American Heritage Dictionary 4
(kə-tălˈĭ-sĭs)
nounpl.ca·tal·y·ses(-sēzˌ)
The action of a catalyst, especially an increase in the rate of a chemical reaction.