Can you give me a brief simple definition for hyperbole and give me a brief example of hyperbole?

Hyperbole means exaggeration. It is from a Greek word meaning 'excess'. So it shows too much description which is not needed, and may not be true in reality.
Some examples are:
“I’ve told you a million times”
(You can't say it a million times, can you???)

“It was so cold, I saw polar bears wearing jackets”
(Where did polar bears jump in from ??? They live near the Poles. They can't come to see you, right??? )

“She is so dumb, she thinks Taco Bell is a Mexican phone company”

Here are some common examples of hyperboles:
I am so hungry I could eat a horse.
I have a million things to do.
I had to walk 15 miles to school in the snow, uphill.
I had a ton of homework.
If I can’t buy that new game, I will die. (Hahah - you won't )
He is as skinny as a toothpick.
This car goes faster than the speed of light.
That new car costs a bazillion dollars.
We are so poor; we don’t have two cents to rub together.
That joke is so old, the last time I heard it I was riding on a dinosaur.
They ran like greased lightning.
He's got tons of money.
You could have knocked me over with a feather.
Her brain is the size of a pea.
He is older than the hills.

NOTE : NONE OF THEM ARE POSSIBLE, SO THEY ARE EXAGGERATED/ OR MADE A BIG MATTER OUT OF A SMALL THING (LIKE THE FAMOUS PROVERB - A STORM IN A TEACUP WHICH MEANS TO EXAGGERATE)