A long and fast talk that tries to get people to do something or to buy something.
A spiel can make people feel annoyed or pressured.
Examples:
The salesman gave us a long spiel about the car.
I don't like it when people give me a spiel about things I don't want.
She always gives the same spiel about her new product.
The teacher gave a funny spiel about why we should do our homework.
The alien gave a crazy spiel about why we should go to space.
I always remember the spiel the man gave about the magic beans.