(chemistry) a substance that initiates or accelerates a chemical reaction without itself being affected
"The platinum acted as a catalyst, speeding up the conversion of nitrogen and oxygen into nitric oxide while remaining unchanged."
something that causes an important event to happen
"the invasion acted as a catalyst to unite the country"
A substance that increases the rate of a chemical reaction without being consumed in the process.
"The platinum acts as a catalyst by speeding up the conversion of carbon monoxide into harmless gases without itself being used up."
In plain English: A catalyst is something that makes an event happen faster without being used up itself.
"The teacher's enthusiasm acted as a catalyst for her students' interest in science."
Usage: While originally describing substances that speed up chemical reactions, this word is commonly used metaphorically to refer to any person or event that precipitates significant change. Use it when you need an agent for transformation rather than simply someone who encourages action.
From catalysis + -ist.