What is the need of term 'closed circuit'? If a circuit is a closed path in which charges can flow then why do we have the term closed circuit? Doesn't the definition mean that a circuit is always closed.
 A: 
why do we have the term closed circuit?

I believe this is a historical use that came about because of switches.
Definitionally, an open circuit is one that is not complete, and a closed circuit is one that is electrically complete. This is not unique to electricity, I've seen some variation on these theme in other places like water flow and even money. And thus your confusion, because it would seem that any circuit is, by definition, closed.
But electrical circuits often include switches. Switches used to be little bars of metal with a pivot at one end and a clasp at the other. It moves like a door seen from above. If you raise the bar the current stops, a motion that is like opening a door. So when the switch is open, you have an open circuit. The term is more like a verb than an adjective in this case; an open circuit is what you get from the action of opening the switch.
A: Simply put when an circuit is "closed" it is not leaking in electricity (electric charges) or the wires are connected and as no electricity is allowed to leave the circuit it is called a "Closed Circuit" and the vice-versa goes for "Open Circuit".
Your welcome. 
