What is catalyst?

I had not understood your question.Which catalyst you want.

Chemically--> catalsy which enhance the rate of reaction without taking part in it.
or
google it.

What Rohit told is the right answer.We call a person who does so also as a catalyst.

It would be interesting to discuss events that have acted like catalysts in history.

Like perhaps how the bombing of Pearl Harbour by Japan acted as a catalyst to USA entering into World War II...

catalyst is a substance which increases the rate of a reaction without being consumed in it.it means the amount of the catalyst remains unchanged and it increase the speed of the reaction.