Catalytic describes something that speeds up a process or a change, especially without being used up itself - this comes from chemistry, where a 'catalyst' is a substance added to a reaction to make it happen faster. The word you'll actually meet most in daily life is 'catalytic converter' - the part in a car's exhaust system that changes harmful gases into less harmful ones before they leave the car. Outside chemistry, people also use 'catalytic' more loosely for anything that triggers fast change.