In the art of negotiation, what is BATNA?

Thanks for the invitation.

BATNA protects to a negotiator from accepting an agreement that is highly un-favorable and without any good interests. This can be defined as a better option outside the negotiation. 

A negotiator's  stronger BATNA means  his stronger strength by having the attractive alternative in case if he cannot reach to an acceptable agreement. 

It is 

 Best Alternative to a Negotiated Agreement