Question

What is an example of Deceleration?

Answer 1

That's a word often used to mean "slowing down". An example is what happens
when the brake is applied in a moving car.

But 'deceleration' is a very unofficial, unscientific word.  If the forward speed
is decreasing, then a much more useful concept is "negative acceleration".

Answer 2

When the body starts moving with a slower speed than the initial speed and it slows down continuously, the this is called deceleration. Examples of deceleration - 

When a ball is thrown upwards, its speed goes on decreasing as its height increases.
When a car applies brakes.