Question

What is memant by closed system? Give example.

Answer 1

A closed system is a physical system that does not allow certain types of transfers (such as transfer of mass and energy transfer) in or out of the system. 

Answer 2

A closed system is meant by the physical system which never exchanges any matter along with its surroundings.

Closed systems are also known as the isolated system which isn't subjected to any net force whose origin is outside to the practice.  

Best example:

If the soup is spilled into an insulated box and closed, there will not be any kind of heat exchange inside it.